The Atlantic slave trade or transatlantic slave trade involved the transportation by slave traders of enslaved African people to the Americas. European slave ships regularly used the triangular trade route and its Middle Passage. Europeans established a coastal slave trade in the 15th century and trade to the Americas began in the 16th century, lasting through the 19th century. The vast majority of those who were transported in the transatlantic slave trade were from Central Africa and West Africa and had been sold by West African slave traders to European slave traders, while others had been captured directly by the slave traders in coastal raids. European slave traders gathered and imprisoned the enslaved at forts on the African coast and then brought them to the Americas. Some Portuguese and Europeans participated in slave raids. As the National Museums Liverpool explains: "European traders captured some Africans in raids along the coast, but bought most of them from local African or African-European dealers." Many European slave traders generally did not participate in slave raids because life expectancy for Europeans in sub-Saharan Africa was less than one year during the period of the slave trade because of malaria that was endemic in the African continent. An article from PBS explains: "Malaria, dysentery, yellow fever, and other diseases reduced the few Europeans living and trading along the West African coast to a chronic state of ill health and earned Africa the name 'white man's grave.' In this environment, European merchants were rarely in a position to call the shots." The earliest known use of the phrase began in the 1830s, and the earliest written evidence was found in an 1836 published book by F. H. Rankin. Portuguese coastal raiders found that slave raiding was too costly and often ineffective and opted for established commercial relations.

The colonial South Atlantic and Caribbean economies were particularly dependent on slave labour for the production of sugarcane and other commodities. This was viewed as crucial by those Western European states which were vying with one another to create overseas empires. The Portuguese, in the 16th century, were the first to transport slaves across the Atlantic. In 1526, they completed the first transatlantic slave voyage to Brazil, and other Europeans soon followed. Shipowners regarded the slaves as cargo to be transported to the Americas as quickly and cheaply as possible, there to be sold to work on coffee, tobacco, cocoa, sugar, and cotton plantations, gold and silver mines, rice fields, the construction industry, cutting timber for ships, as skilled labour, and as domestic servants. The first enslaved Africans sent to the English colonies were classified as indentured servants, with legal standing similar to that of contract-based workers coming from Britain and Ireland. However, by the middle of the 17th century, slavery had hardened as a racial caste, with African slaves and their future offspring being legally the property of their owners, as children born to slave mothers were also slaves (partus sequitur ventrem). As property, the people were considered merchandise or units of labour, and were sold at markets with other goods and services.

The major Atlantic slave trading nations, in order of trade volume, were Portugal, Britain, Spain, France, the Netherlands, the United States, and Denmark. Several had established outposts on the African coast, where they purchased slaves from local African leaders. These slaves were managed by a factor, who was established on or near the coast to expedite the shipping of slaves to the New World. Slaves were imprisoned in a factory while awaiting shipment. Current estimates are that about 12 million to 12.8 million Africans were shipped across the Atlantic over a span of 400 years. The number purchased by the traders was considerably higher, as the passage had a high death rate, with between 1.2 and 2.4 million dying during the voyage, and millions more in seasoning camps in the Caribbean after arrival in the New World. Millions of people also died as a result of slave raids, wars, and during transport to the coast for sale to European slave traders. Near the beginning of the 19th century, various governments acted to ban the trade, although illegal smuggling still occurred. It was generally thought that the transatlantic slave trade ended in 1867, but evidence was later found of voyages until 1873. In the early 21st century, several governments issued apologies for the transatlantic slave trade.

The Atlantic slave trade developed after trade contacts were established between the "Old World" (Afro-Eurasia) and the "New World" (the Americas). For centuries, tidal currents had made ocean travel particularly difficult and risky for the ships that were then available. Thus, there had been very little, if any, maritime contact between the peoples living in these continents. In the 15th century, however, new European developments in seafaring technologies, such as the invention of the caravel, resulted in ships being better equipped to deal with the tidal currents, and could begin traversing the Atlantic Ocean; the Portuguese set up a Navigator's School (although there is much debate about whether it existed and if it did, just what it was). Between 1600 and 1800, approximately 300,000 sailors engaged in the slave trade visited West Africa. In doing so, they came into contact with societies living along the west African coast and in the Americas which they had never previously encountered. Historian Pierre Chaunu termed the consequences of European navigation "disenclavement", with it marking an end of isolation for some societies and an increase in inter-societal contact for most others.

Historian John Thornton noted, "A number of technical and geographical factors combined to make Europeans the most likely people to explore the Atlantic and develop its commerce". He identified these as being the drive to find new and profitable commercial opportunities outside Europe. Additionally, there was the desire to create an alternative trade network to that controlled by the Muslim Ottoman Empire of the Middle East, which was viewed as a commercial, political and religious threat to European Christendom. In particular, European traders wanted to trade for gold, which could be found in western Africa, and to find a maritime route to "the Indies" (India), where they could trade for luxury goods such as spices without having to obtain these items from Middle Eastern Islamic traders.

During the first wave of European colonization, although many of the initial Atlantic naval explorations were led by the Iberian conquistadors, members of many European nationalities were involved, including sailors from Spain, Portugal, France, England, the Italian states, and the Netherlands. This diversity led Thornton to describe the initial "exploration of the Atlantic" as "a truly international exercise, even if many of the dramatic discoveries were made under the sponsorship of the Iberian monarchs". That leadership later gave rise to the myth that "the Iberians were the sole leaders of the exploration".

European overseas expansion led to the contact between the Old and New Worlds producing the Columbian exchange, named after the Italian explorer Christopher Columbus. It started the global silver trade from the 16th to 18th centuries and led to direct European involvement in the Chinese porcelain trade. It involved the transfer of goods unique to one hemisphere to another. Europeans brought cattle, horses, and sheep to the New World, and from the New World Europeans received tobacco, potatoes, tomatoes, and maize. Other items and commodities becoming important in global trade were the tobacco, sugarcane, and cotton crops of the Americas, along with the gold and silver brought from the American continent not only to Europe but elsewhere in the Old World.

By the 15th century, slavery had existed in the Iberian Peninsula (Portugal and Spain) of Western Europe throughout recorded history. The Roman Empire had established its system of slavery in ancient times. Historian Benjamin Isaac suggests proto-racism existed in ancient times among Greco-Roman people. Racial prejudices were based on dehumanizing the foreign peoples they conquered through warfare. Since the fall of the Western Roman Empire, various systems of slavery continued in the successor Islamic and Christian kingdoms of the peninsula through the early modern era of the Atlantic slave trade. In 1441–1444, Portuguese traders first captured Africans on the Atlantic coast of Africa (in what is today Mauritania), taking their captives to slavery in Europe, and established a fort for the slave trade at the Bay of Arguin.

In the Middle Ages, religion and not race was a determining factor for who was considered to be a legitimate target of slavery. While Christians did not enslave Christians and Muslims did not enslave Muslims, both allowed the enslavement of people they regarded to be heretics or insufficiently correct in their religion, which allowed Catholic Christians to enslave Orthodox Christians, and Sunni Muslims to enslave Shia Muslims; similarly both Christians and Muslims approved of enslaving Pagans, who came to be a preferred and comparatively profitable target of the slave trade in the Middle Ages: Spain and Portugal were provided with non-Catholic slaves from Eastern Europe via the Balkan slave trade and the Black Sea slave trade.

In the 15th century, when the Balkan slave trade was taken over by the Ottoman Empire and the Black Sea slave trade was supplanted by the Crimean slave trade and closed off from Europe, Spain and Portugal replaced this source of slaves by importing slaves first from the conquered Canary Islands and then from mainland Africa, initially from Arab slave traders via the Trans-Saharan slave trade from Libya, and then directly from the African West coast through Portuguese outposts, which developed into the Atlantic slave trade and expanded significantly after the establishment of the colonies in the Americas in 1492.

In the 15th century, Spain enacted a racially discriminatory law named limpieza de sangre, which translates as "blood purity" or "cleanliness of blood", a proto-racial law. It prevented people with Jewish and Muslim ancestry from settling in the New World. Limpieza de sangre did not guarantee rights for Jews or Muslims who converted to Catholicism. Jews and Muslims who converted to Catholicism were respectively called conversos and moriscos. Some Jews and Muslims converted to Christianity hoping it would grant them rights under Spanish laws. After the "discovery" of new lands across the Atlantic, Spain did not want Jews and Muslims immigrating to the Americas because the Spanish Crown worried Muslims and non-Christians might introduce Islam and other religions to Native Americans. The law also led to the enslavement of Jews and Muslims, prevented Jews from entering the country and from joining the military, universities and other civil services. Although Jewish conversos and Muslims experienced religious and racial discrimination, some also participated in the slave trade of Africans. In Lisbon during the 16th and 17th centuries, Muslims financed by Jewish conversos traded Africans across the Sahara Desert and enslaved Africans before and during the Atlantic slave trade in Europe and Africa. In New Spain, Spaniards applied limpieza de sangre to Africans and Native Americans and created a racial caste system, believing them to be impure because they were not Christian.

Europeans enslaved Muslims and people practicing other religions as a justification to Christianize them. In 1452, Pope Nicholas V issued papal bull Dum Diversas which gave the King of Portugal the right to enslave non-Christians to perpetual slavery. The clause included Muslims in West Africa and legitimized the slave trade under the Catholic church. In 1454, Pope Nicholas issued Romanus Pontifex. "Written as a logical sequel to Dum Diversas, Romanus Pontifex allowed the European Catholic nations to expand their dominion over 'discovered' land. Possession of non-Christian lands would be justified along with the enslavement of native, non-Christian 'pagans' in Africa and the 'New World.'" Dum Diversas and Romanus Pontifex may have had an influence with the creation of doctrines supportive of empire building.

In 1493, the Doctrine of Discovery issued by Pope Alexander VI, was used as a justification by Spain to take lands from non-Christians West of the Azores. The Doctrine of Discovery stated that non-Christian lands should be taken and ruled by Christian nations, and Indigenous people (Africans and Native Americans) living on their lands should convert to Christianity. In 1493, Pope Alexander VI issued a papal bull called Inter Caetera which gave Spain and Portugal rights to claim and colonize all non-Christian lands in the Americas and enslave Native Americans and Africans. Inter Caetera also settled a dispute between Portugal and Spain over those lands. The declaration included a north–south divide 100 leagues West of the Cape Verde Islands and gave the Spanish Crown exclusive rights to travel and trade west of that line.

In Portugal and Spain people had been enslaved because of their religious identity, race had not been a developed factor for enslaving people; nonetheless, by the 15th century, Europeans used both race and religion as a justification to enslave sub-Saharan Africans. An increase of enslaved African people from Senegal occurred in the Iberian Peninsula in the 15th century. As the number of Senegalese slaves grew larger Europeans developed new terminologies that associated slavery with skin color. The Spanish city of Seville had the largest African population. "The Treaty of Alcacuvas in 1479 provided traders the right to supply Spaniards with Africans."

In addition, in the 15th century, Dominican friar Annius of Viterbo invoked the Curse of Ham, from the biblical story of enslavement, to explain the differences between Europeans and Africans in his writings. Annius, who frequently wrote of the "superiority of Christians over the Saracens", claimed that due to the curse imposed upon Black people, they would inevitably remain permanently subjugated by Arabs and other Muslims. He wrote that the fact that so many Africans had been enslaved even by the heretical Muslims was supposed proof of their inferiority. Through these and other writings, European writers established a hitherto unheard of connection between a cursed people, Africa and slavery, which laid the ideological groundwork for justifying the transatlantic slave trade. The term "race" was used by the English beginning in the 16th century and referred to family, lineage, and breed. The idea of race continued to develop further through the centuries and was used as a justification for the continuation of the slave trade and racial discrimination.

Slavery was prevalent in many parts of Africa for many centuries before the beginning of the Atlantic slave trade. An article from PBS explains the differences between African slavery and European slavery in the Americas. "It is important to distinguish between European slavery and African slavery. In most cases, slavery systems in Africa were more like indentured servitude in that the slaves retained some rights and children born to slaves were generally born free. The slaves could be released from servitude and join a family clan. In contrast, European slaves were chattel, or property, who were stripped of their rights. The cycle of slavery was perpetual; children of slaves would, by default, also be slaves."

Millions of enslaved people from some parts of Africa were exported to states in Africa, Europe, and Asia prior to the European colonization of the Americas. The Trans-Saharan slave trade across the Sahara had functioned since antiquity, and continued to do so up until the 20th-century; in 652, the Rashidun Caliphate in Egypt enforced an annual tribute of 400 slaves from the Christian Kingdom of Makuria by the Baqt treaty, which was to be in effect for centuries. It supplied Africans for slavery in the Rashidun Caliphate (632–661), the Umayyad Caliphate (661–750), the Abbasid Caliphate (750–1258) and the Mamluk Sultanate.

The Atlantic slave trade was not the only slave trade from Africa; as Elikia M'bokolo wrote in Le Monde diplomatique:

The African continent was bled of its human resources via all possible routes. Across the Sahara, through the Red Sea, from the Indian Ocean ports and across the Atlantic. At least ten centuries of slavery for the benefit of the Muslim countries (from the ninth to the nineteenth) ... Four million enslaved people exported via the Red Sea, another four million through the Swahili ports of the Indian Ocean, perhaps as many as nine million along the trans-Saharan caravan route, and eleven to twenty million (depending on the author) across the Atlantic Ocean.

Slaves were marched in shackles to the coasts of Sudan, Ethiopia and Somali, placed upon dhows and trafficked across the Indian Ocean to the Gulf or Aden. Others were carried across the Red Sea to Arabia and Aden, with sick slaves being thrown overboard, or they were marched across the Sahara desert via the Trans-Saharan slave trade route to the Nile, many of them dying from exposure or swollen feet along the way.

However, estimates are imprecise, which can affect comparison between different slave trades. Two rough estimates by scholars of the numbers African slaves held over twelve centuries in the Muslim world are 11.5 million and 14 million, while other estimates indicate a number between 12 and 15 million African slaves prior to the 20th century.

According to John K. Thornton, Europeans usually bought enslaved people who had been captured in endemic warfare between African states. Some Africans had made a business out of capturing war captives or members of neighboring ethnic groups and selling them. A reminder of this practice is documented in the Slave Trade Debates of England in the early 19th century: "All the old writers ... concur in stating not only that wars are entered into for the sole purpose of making slaves, but that they are fomented by Europeans, with a view to that object." People living around the Niger River would be transported from these markets to the coast and sold in European trading ports, in exchange for muskets and manufactured goods such as cloth or alcohol. The European demand for slaves provided a new and larger market for the already existing trade. While those held as slaves in their own region of Africa could hope to escape, those shipped away had little chance of returning to their homeland.

The Atlantic slave trading of Africans began in 1441 with two Portuguese explorers, Nuno Tristão and António Gonçalves. Tristão and Gonçalves sailed to Mauritania in West Africa and kidnapped twelve Africans and returned to Portugal and presented the captive Africans as gifts to Prince Henry the Navigator. By 1460, seven hundred to eight hundred African people were taken annually and imported into Portugal. In Portugal, the Africans taken were used as domestic servants. From 1460 to 1500, the removal of Africans increased as Portugal and Spain built forts along the coast of West Africa. By 1500, Portugal and Spain had taken about 50,000 thousand West Africans. The Africans worked as domestic servants, artisans, and farmers. Other Africans were taken to work the sugar plantations on the Azores, Madeira, Canary, and Cape Verde islands. Europeans participated in African enslavement because of their need for labor, profit, and religious motives.

Upon discovering new lands through their naval explorations, European colonisers soon began to migrate to and settle in lands outside their native continent. Off the coast of Africa, European migrants, under the directions of the Kingdom of Castile, invaded and colonised the Canary Islands during the 15th century, where they converted much of the land to the production of wine and sugar. Along with this, they also captured native Canary Islanders, the Guanches, to use as slaves both on the Islands and across the Christian Mediterranean.

After the success of Portugal and Spain in the slave trade other European nations followed. In 1530, an English merchant from Plymouth, William Hawkins, visited the Guinea Coast and left with a few slaves. In 1564, Hawkin's son John Hawkins, sailed to the Guinea Coast and his voyage was supported by Queen Elizabeth I. John later turned to piracy and stole 300 Africans from a Spanish slave ship after failures in Guinea trying to capture Africans as most of his men died after fights with the local Africans.

As historian John Thornton remarked, "the actual motivation for European expansion and for navigational breakthroughs was little more than to exploit the opportunity for immediate profits made by raiding and the seizure or purchase of trade commodities". Using the Canary Islands as a naval base, Europeans, at the time primarily Portuguese traders, began to move their activities down the western coast of Africa, performing raids in which slaves would be captured to be later sold in the Mediterranean. Although initially successful in this venture, "it was not long before African naval forces were alerted to the new dangers, and the Portuguese [raiding] ships began to meet strong and effective resistance", with the crews of several of them being killed by African sailors, whose boats were better equipped at traversing the west-central African coasts and river systems.

By 1494, the Portuguese king had entered agreements with the rulers of several West African states that would allow trade between their respective peoples, enabling the Portuguese to "tap into" the "well-developed commercial economy in Africa ... without engaging in hostilities". "Peaceful trade became the rule all along the African coast", although there were some rare exceptions when acts of aggression led to violence. For instance, Portuguese traders attempted to conquer the Bissagos Islands in 1535. In 1571, Portugal, supported by the Kingdom of Kongo, took control of the south-western region of Angola in order to secure its threatened economic interest in the area. Although Kongo later joined a coalition in 1591 to force the Portuguese out, Portugal had secured a foothold on the continent that it continued to occupy until the 20th century. Despite these incidents of occasional violence between African and European forces, many African states ensured that any trade went on in their own terms, for instance, imposing custom duties on foreign ships. In 1525, the Kongolese King Afonso I seized a French vessel and its crew for illegally trading on his coast. In addition, Afonso complained to the king of Portugal that Portuguese slave traders continued to kidnap his people, which was causing depopulation in his kingdom. Queen Nzinga (Nzinga Mbande) fought against the expansion of the Portuguese slave trade into Mbundu people's lands in Central Africa in the 1620s. The Portuguese encroached onto Mbundu lands to expand their mission of trading slaves and establishing a settlement. Nzinga allowed sanctuary to runaway slaves in her nation and organized a military called kilombo against the Portuguese. Nzinga formed alliances with other rival African nations and led an army against the Portuguese slave traders in a thirty-year war.

Historians have widely debated the nature of the relationship between these African kingdoms and the European traders. The Guyanese historian Walter Rodney (1972) has argued that it was an unequal relationship, with Africans being forced into a "colonial" trade with the more economically developed Europeans, exchanging raw materials and human resources (i.e. slaves) for manufactured goods. He argued that it was this economic trade agreement dating back to the 16th century that led to Africa being underdeveloped in his own time. These ideas were supported by other historians, including Ralph Austen (1987). This idea of an unequal relationship was contested by John Thornton (1998), who argued that "the Atlantic slave trade was not nearly as critical to the African economy as these scholars believed" and that "African manufacturing [at this period] was more than capable of handling competition from preindustrial Europe". However, Anne Bailey, commenting on Thornton's suggestion that Africans and Europeans were equal partners in the Atlantic slave trade, wrote:

[T]o see Africans as partners implies equal terms and equal influence on the global and intercontinental processes of the trade. Africans had great influence on the continent itself, but they had no direct influence on the engines behind the trade in the capital firms, the shipping and insurance companies of Europe and America, or the plantation systems in Americas. They did not wield any influence on the building manufacturing centres of the West.

Sometimes trading between Europeans and African leaders was not equal. For example, Europeans influenced Africans to provide more slaves by forming military alliances with warring African societies to instigate more fighting which would provide more war captives to the African rulers to trade as slaves for European consumer goods. Also, Europeans shifted the location of disembarkation points for trade along the African coast to follow military conflicts in West-Central Africa. In areas of Africa where slavery was not prevalent, European slave traders worked and negotiated with African rulers on their terms for trade, and African rulers refused to supply European demands. Africans and Europeans profited from the slave trade; however, African populations, the social, political, and military changes to African societies suffered greatly. For example, Mossi Kingdoms resisted the Atlantic slave trade and refused to participate in the selling of African people. However, as time progressed more European slave traders entered into West Africa and were having more influence in African nations and the Mossi became involved in slave trading in the 1800s.

Although there were African nations that participated and profited from the Atlantic slave trade, many African nations resisted such as the Djola and Balanta. Some African nations organized into military resistance movements and fought African slave raiders and European slave traders entering their villages. For example, the Akan, Etsi, Fetu, Eguafo, Agona, and Asebu people organized into the Fante coalition and fought African and European slave raiders and protected themselves from capture and enslavement. Chief Tomba was born in 1700 and his adopted father was a general from the Jalonke-speaking people who fought against the slave trade. Tomba became ruler of the Baga people in present-day Guinea Bissau in West Africa and made alliances with nearby African villages against African and European slave traders. His efforts were unsuccessful: Tomba was captured by African traders and sold into slavery.

Dahomey King Agaja from 1718 to 1740, opposed the Atlantic slave trade and refused to sell African people and attacked the European forts built along the slave coast in West Africa. Donna Beatriz Kimpa Vita in Kongo and Senegalese leader Abd al-Qadir, advocated resistance against the forced exportation of Africans. In the 1770s, leader Abdul Kader Khan opposed the Atlantic slave trade through Futa Toro, present-day Senegal. Abdul Kader Khan and Futa Toro nation resisted French slave traders and colonizers who wanted to enslave Africans and Muslims from Futa Toro. Other forms of resistance against the Atlantic slave trade by African nations was migrating to different areas in West Africa such as swamps and lake regions to escape slave raids. In West Africa, Efik slave dealers participated in slave dealing as a form of protection against enslavement. African resistance movements were carried out in every phase of the slave trade to resisting marches to the slave holding stations, resistance at the slave coast, and resistance on slave ships.

For example, aboard the slave ship Clare, the enslaved Africans revolted and drove the crew from the vessel and took control of the ship and liberated themselves and landed near Cape Coast Castle in present-day Ghana in 1729. On other slave ships enslaved Africans sunk ships, killed the crew, and set fire to ships with explosives. Slave traders and white crewmembers prepared and prevented possible rebellions by loading women, men, and children separately inside slave ships because enslaved children used loose pieces of wood, tools, and any objects they found and passed them to the men to free themselves and fight the crew. According to historical research from the records of slave ship captains, between 1698 and 1807, there were 353 acts of insurrection aboard slave ships. The majority of the rebellions by the Africans were defeated. Igbo slaves on ships committed suicide by jumping overboard as an act of resistance to enslavement. To prevent further suicides, white crewmen placed nets around slave ships to catch enslaved persons that jumped overboard. White captains and crewmen invested in firearms, swivel guns, and ordered ship crews to watch slaves to prevent or prepare for possible slave revolts. John Newton was a captain of slave ships and recorded in his personal journal how Africans mutinied on ships, and some were successful in overtaking the crew. For example, in 1730 the slave ship Little George departed from the Guinea Coast in route to Rhode Island with a cargo of ninety-six enslaved Africans. A few of the slaves slipped out of their iron chains and killed three of the watchmen on deck and imprisoned the captain and the rest of the crew. The captain and crew made a deal with the Africans and promised them their freedom. The Africans took control of the ship and sailed back to Africa's shore. The captain and his crew tried to re-enslave the Africans but were unsuccessful.

The Atlantic slave trade is customarily divided into two eras, known as the first and second Atlantic systems. Slightly more than 3% of the enslaved people exported from Africa were traded between 1525 and 1600, and 16% in the 17th century.

The first Atlantic system was the trade of enslaved Africans to, primarily, American colonies of the Portuguese and Spanish empires. Before the 1520s, slavers took Africans to Seville or the Canary Islands and then exported some of them from Spain to its colonies in Hispaniola and Puerto Rico, with 1 to 40 slaves per ship. These supplemented enslaved Native Americans. In 1518, the Spanish king gave permission for ships to go directly from Africa to the Caribbean colonies, and they started taking 200-300 per trip.

During the first Atlantic system, most of these slavers were Portuguese, giving them a near-monopoly. Decisive was the 1494 Treaty of Tordesillas which did not allow Spanish ships in African ports. Spain had to rely on Portuguese ships and sailors to bring slaves across the Atlantic. From 1525, slaves were transported directly from the Portuguese colony of Sao Tomé across the Atlantic to Hispaniola.

A burial ground in Campeche, Mexico, suggests enslaved Africans had been brought there not long after Hernán Cortés completed the subjugation of Aztec and Mayan Mexico in 1519. The graveyard had been in use from approximately 1550 to the late 17th century.

In 1562, John Hawkins captured Africans in what is now Sierra Leone and took 300 people to sell in the Caribbean. In 1564, he repeated the process, this time using Queen Elizabeth's own ship, Jesus of Lübeck, and numerous English voyages ensued.

Around 1560, the Portuguese began a regular slave trade to Brazil. From 1580 until 1640, Portugal was temporarily united with Spain in the Iberian Union. Most Portuguese contractors who obtained the asiento between 1580 and 1640 were conversos. For Portuguese merchants, many of whom were "New Christians" or their descendants, the union of crowns presented commercial opportunities in the slave trade to Spanish America.

Until the middle of the 17th century, Mexico was the largest single market for slaves in Spanish America. While the Portuguese were directly involved in trading enslaved peoples to Brazil, the Spanish Empire relied on the Asiento de Negros system, awarding (Catholic) Genoese merchant bankers the license to trade enslaved people from Africa to their colonies in Spanish America. Cartagena, Veracruz, Buenos Aires, and Hispaniola received the majority of slave arrivals, mainly from Angola. This division of the slave trade between Spain and Portugal upset the British and the Dutch who invested in the British West Indies and Dutch Brazil producing sugar. After the Iberian Union fell apart, Spain prohibited Portugal from directly engaging in the slave trade as a carrier. According the Treaty of Münster the slave trade was opened for the traditional enemies of Spain, losing a large share of the trade to the Dutch, French, and English. For 150 years, Spanish transatlantic traffic was operating at trivial levels. In many years, not a single Spanish slave voyage set sail from Africa. Unlike all of their imperial competitors, the Spanish almost never delivered slaves to foreign territories. By contrast, the British, and the Dutch before them, sold slaves everywhere in the Americas.

The second Atlantic system was the trade of enslaved Africans by mostly English, French, and Dutch traders and investors. The main destinations of this phase were the Caribbean islands Curaçao, Jamaica and Martinique, as European nations built up economically slave-dependent colonies in the New World. In 1672, the Royal Africa Company was founded. In 1674, the New West India Company became deeper involved in slave trade. From 1677, the Compagnie du Sénégal, used Gorée to house the slaves. The Spanish proposed to get the slaves from Cape Verde, located closer to the demarcation line between the Spanish and Portuguese empire, but this was against the WIC-charter". The Royal African Company usually refused to deliver slaves to Spanish colonies, though they did sell them to all comers from their factories in Kingston, Jamaica and Bridgetown, Barbados. In 1682, Spain allowed governors from Havana, Porto Bello, Panama, and Cartagena, Colombia to procure slaves from Jamaica.

By the 1690s, the English were shipping the most slaves from West Africa. By the 18th century, Portuguese Angola had become again one of the principal sources of the Atlantic slave trade. After the end of the War of the Spanish Succession, as part of the provisions of the Treaty of Utrecht (1713), the Asiento was granted to the South Sea Company. Despite the South Sea Bubble, the British maintained this position during the 18th century, becoming the biggest shippers of slaves across the Atlantic. It is estimated that more than half of the entire slave trade took place during the 18th century, with the Portuguese, British, and French being the main carriers of nine out of ten slaves abducted in Africa. At the time, slave trading was regarded as crucial to Europe's maritime economy, as noted by one English slave trader: "What a glorious and advantageous trade this is ... It is the hinge on which all the trade of this globe moves."

Meanwhile, it became a business for privately owned enterprises, reducing international complications. After 1790, by contrast, captains typically checked out slave prices in at least two of the major markets of Kingston, Havana, and Charleston, South Carolina (where prices by then were similar) before deciding where to sell. For the last sixteen years of the transatlantic slave trade, Spain was the only transatlantic slave-trading empire.

Following the British Slave Trade Act 1807 and U.S. bans on the African slave trade that same year, it declined, but the period thereafter still accounted for 28.5% of the total volume of the Atlantic slave trade. Between 1810 and 1860, over 3.5 million slaves were transported, with 850,000 in the 1820s.

The first side of the triangle was the export of goods from Europe to Africa. A number of African kings and merchants took part in the trading of enslaved people from 1440 to about 1833. For each captive, the African rulers would receive a variety of goods from Europe. These included guns, ammunition, alcohol, indigo dyed Indian textiles, and other factory-made goods. The second leg of the triangle exported enslaved Africans across the Atlantic Ocean to the Americas and the Caribbean Islands. The third and final part of the triangle was the return of goods to Europe from the Americas. The goods were the products of slave plantations and included cotton, sugar, tobacco, molasses and rum. Sir John Hawkins, considered the pioneer of the English slave trade, was the first to run the triangular trade, making a profit at every stop.

The Atlantic slave trade was the result of, among other things, labour shortage, itself in turn created by the desire of European colonists to exploit New World land and resources for capital profits. Native peoples were at first utilized as slave labour by Europeans until a large number died from overwork and Old World diseases. Furthermore, in the mid-16th century, the Spanish New Laws, prohibited slavery of the Indigenous people. A labour shortage resulted. Alternative sources of labour, such as indentured servitude, failed to provide a sufficient workforce. Many crops could not be sold for profit, or even grown, in Europe. Exporting crops and goods from the New World to Europe often proved to be more profitable than producing them on the European mainland. A vast amount of labour was needed to create and sustain plantations that required intensive labour to grow, harvest, and process prized tropical crops. Western Africa (part of which became known as "the Slave Coast"), Angola and nearby Kingdoms and later Central Africa, became the source for enslaved people to meet the demand for labour.

The basic reason for the constant shortage of labour was that, with much cheap land available and many landowners searching for workers, free European immigrants were able to become landowners themselves relatively quickly, thus increasing the need for workers. Labour shortages were mainly met by the English, French and Portuguese with African slave labour.

Thomas Jefferson attributed the use of slave labour in part to the climate, and the consequent idle leisure afforded by slave labour: "For in a warm climate, no man will labour for himself who can make another labour for him. This is so true, that of the proprietors of slaves a very small proportion indeed are ever seen to labour." In a 2015 paper, economist Elena Esposito argued that the enslavement of Africans in colonial America was attributable to the fact that the American south was sufficiently warm and humid for malaria to thrive; the disease had debilitating effects on the European settlers. Conversely, many enslaved Africans were taken from regions of Africa which hosted particularly potent strains of the disease, so the Africans had already developed natural resistance to malaria. This, Esposito argued, resulted in higher malaria survival rates in the American south among enslaved Africans than among European labourers, making them a more profitable source of labour and encouraging their use.

Historian David Eltis argues that Africans were enslaved because of cultural beliefs in Europe that prohibited the enslavement of cultural insiders, even if there was a source of labour that could be enslaved (such as convicts, prisoners of war and vagrants). Eltis argues that traditional beliefs existed in Europe against enslaving Christians (few Europeans not being Christian at the time) and those slaves that existed in Europe tended to be non-Christians and their immediate descendants (since a slave converting to Christianity did not guarantee emancipation) and thus by the 15th century Europeans as a whole came to be regarded as insiders. Eltis argues that while all slave societies have demarked insiders and outsiders, Europeans took this process further by extending the status of insider to the entire European continent, rendering it unthinkable to enslave a European since this would require enslaving an insider. Conversely, Africans were viewed as outsiders and thus qualified for enslavement. While Europeans may have treated some types of labour, such as convict labour, with conditions similar to that of slaves, these labourers would not be regarded as chattel and their progeny could not inherit their subordinate status, thus not making them slaves in the eyes of Europeans. The status of chattel slavery was thus confined to non-Europeans, such as Africans.

For the British, slaves were no more than animals and could be treated as commodities, so situations like the Zong massacre occurred without any justice for the victims.

African partners, including rulers, traders and military aristocrats, played a direct role in the slave trade. They sold slaves acquired from wars or through kidnapping to Europeans or their agents. Those sold into slavery were usually from a different ethnic group than those who captured them, whether enemies or just neighbors. These captive slaves were considered "other", not part of the people of the ethnic group or "tribe"; African kings were only interested in protecting their own ethnic group, but sometimes criminals would be sold to get rid of them. Most other slaves were obtained from kidnappings, or through raids that occurred at gunpoint through joint ventures with the Europeans. The kingdom of Dahomey supplied war captives to European slave traders.

According to Pernille Ipsen, author of Daughters of the Trade: Atlantic Slavers and Interracial Marriage on the Gold Coast, Africans from the Gold Coast (present-day Ghana) also participated in the slave trade through intermarriage, or cassare (taken from Italian, Spanish, or Portuguese), meaning 'to set up house'. It is derived from the Portuguese word 'casar', meaning 'to marry'. Cassare formed political and economic bonds between European and African slave traders. Cassare was a pre-European-contact practice used to integrate the "other" from a differing African tribe. Early on in the Atlantic slave trade, it was common for the powerful elite West African families to marry off their women to the European traders in alliance, bolstering their syndicate. The marriages were even performed using African customs, which Europeans did not object to, seeing how important the connections were.

It is difficult to reconstruct and generalize how Africans residing in Africa understood the Atlantic slave trade, though there is evidence for some societies that African elites and slave traders had awareness of the conditions of the slaves who were transported to the Americas. According to Robin Law, the royal elites of the kingdom of Dahomey must have had an "informed understanding" of the fates of the Africans they sold into slavery. Dahomey sent diplomats to Brazil and Portugal who returned with information about their trips. In addition, a few royal elites of Dahomey had experienced slavery for themselves in the Americas before returning to their homeland. The only apparent moral issue that the kingdom had with slavery was the enslavement of fellow Dahomeyans, an offense punishable by death, rather than the institution of slavery itself.

On the Gold Coast, it was common for slave-trading African rulers to encourage their children to learn about Europeans by sending them to sail on European ships, live inside European forts, or travel to Europe or America for an education. Diplomats also traveled to European capital cities. The elites even rescued fellow elites who were tricked into slavery in the Americas by sending demands to the Dutch and the British governments, who complied due to fears of reduced trade and physical harm to hostages. An example is the case of William Ansah Sessarakoo, who was rescued from slavery in Barbados after being recognised by a visiting slave trader of the same Fante ethnic group, and later became a slave trader himself.

Fenda Lawrence was a slave trader from the Gambia who lived and traded in Georgia and South Carolina as a free person.

A common assumption by Africans who were unaware of the true purpose of the Atlantic slave trade was that the Europeans were cannibals who planned on cooking and eating their captives. This rumour was a common source of significant distress for enslaved Africans.

Europeans provided the market for slaves, rarely traveling beyond the coast or entering the African interior, due to fear of disease and native resistance. They typically resided in fortresses on the coasts, where they waited for Africans to provide them captured slaves from the interior in exchange for goods. Cases of European merchants kidnapping free Africans into slavery often resulted in fierce retaliation from Africans, who could momentarily stop trade and even capture or kill Europeans. Europeans who desired safe and uninterrupted trade aimed to prevent kidnapping incidents, and the British passed the "Acts of Parliament for Regulating the Slave Trade" in 1750 which outlawed the abduction of free Africans by "fraud, force, or violence". According to a source from the Lowcountry Digital Library at the College of Charleston, "When Portuguese, and later their European competitors, found that peaceful commercial relations alone did not generate enough enslaved Africans to fill the growing demands of the trans-Atlantic slave trade, they formed military alliances with certain African groups against their enemies. This encouraged more extensive warfare to produce captives for trading."

In 1778, Thomas Kitchin estimated that Europeans were bringing an estimated 52,000 slaves to the Caribbean yearly, with the French bringing the most Africans to the French West Indies (13,000 out of the yearly estimate). The Atlantic slave trade peaked in the last two decades of the 18th century, during and following the Kongo Civil War. Wars among tiny states along the Niger River's Igbo-inhabited region and the accompanying banditry also spiked in this period. Another reason for surplus supply of enslaved people was major warfare conducted by expanding states, such as the kingdom of Dahomey, the Oyo Empire, and the Ashanti Empire.

Forms of slavery varied both in Africa and in the New World. In general, slavery in Africa was not heritable—that is, the children of slaves were free—while in the Americas, children of slave mothers were considered born into slavery. This was connected to another distinction: slavery in West Africa was not reserved for racial or religious minorities, as it was in European colonies, although the case was otherwise in places such as Somalia, where Bantus were taken as slaves for the ethnic Somalis.

The treatment of slaves in Africa was more variable than in the Americas. At one extreme, the kings of Dahomey routinely slaughtered slaves in hundreds or thousands in sacrificial rituals, and slaves as human sacrifices were also known in Cameroon. On the other hand, slaves in other places were often treated as part of the family, "adopted children", with significant rights including the right to marry without their masters' permission. Scottish explorer Mungo Park wrote:

The slaves in Africa, I suppose, are nearly in the proportion of three to one to the freemen. They claim no reward for their services except food and clothing, and are treated with kindness or severity, according to the good or bad disposition of their masters ... The slaves which are thus brought from the interior may be divided into two distinct classes—first, such as were slaves from their birth, having been born of enslaved mothers; secondly, such as were born free, but who afterwards, by whatever means, became slaves. Those of the first description are by far the most numerous ...

In the Americas, slaves were denied the right to marry freely and masters did not generally accept them as equal members of the family. New World slaves were considered the property of their owners, and slaves convicted of revolt or murder were executed.

Europeans would buy and ship slaves to the Western Hemisphere from markets across West Africa. The number of enslaved people sold to the New World varied throughout the slave trade. As for the distribution of slaves from regions of activity, certain areas produced far more enslaved people than others. Between 1650 and 1900, 10.2 million enslaved Africans arrived in the Americas from the following regions in the following proportions:

• Senegambia (Senegal and the Gambia): 4.8%
• Upper Guinea (Guinea-Bissau, Guinea and Sierra Leone): 4.1%
• Windward Coast (Liberia and Ivory Coast): 1.8%
• Gold Coast (Ghana and east of Ivory Coast): 10.4%
• Bight of Benin (Togo, Benin and Nigeria west of the Niger Delta): 20.2%
• Bight of Biafra (Nigeria east of the Niger Delta, Cameroon, Equatorial Guinea and Gabon): 14.6%
• West Central Africa (Republic of the Congo, Democratic Republic of the Congo and Angola): 39.4%
• Southeastern Africa (Mozambique and Madagascar): 4.7%

Although the slave trade was largely global, there was considerable intracontinental slave trade in which 8 million people were enslaved within the African continent. Of those who did move out of Africa, 8 million were forced out of Eastern Africa to be sent to Asia.

There were over 173 city-states and kingdoms in the African regions affected by the slave trade between 1502 and 1853, when Brazil became the last Atlantic import nation to outlaw the slave trade. Of those 173, no fewer than 68 could be deemed nation-states with political and military infrastructures that enabled them to dominate their neighbours. Nearly every present-day nation had a pre-colonial predecessor, sometimes an African empire with which European traders had to barter.

The different ethnic groups brought to the Americas closely correspond to the regions of heaviest activity in the slave trade. Over 45 distinct ethnic groups were taken to the Americas during the trade. Of the 45, the ten most prominent, according to slave documentation of the era and modern genealogical studies are listed below.

1. The BaKongo of the Democratic Republic of Congo, the Republic of the Congo and Angola
2. The Mandé of Upper Guinea
3. The Gbe speakers of Togo, Ghana, and Benin (Fon, Ewe, Adja, Mina)
4. The Akan of Ghana and Ivory Coast
5. The Wolof of Senegal and the Gambia
6. The Igbo of southeastern Nigeria
7. The Ambundu of Angola
8. The Yoruba of southwestern Nigeria and Benin
9. The Tikar and Bamileke of Cameroon
10. The Makua of Mozambique

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The transatlantic slave trade resulted in a vast and as yet unknown loss of life for African captives both in and outside the Americas. Estimates have ranged from as low as 2 million to as high 60 million. "More than a million people are thought to have died" during their transport to the New World according to a BBC report. More died soon after their arrival. The number of lives lost in the procurement of slaves remains a mystery but may equal or exceed the number who survived to be enslaved.

The trade led to the destruction of individuals and cultures. Historian Ana Lucia Araujo has noted that the process of enslavement did not end with arrival on Western Hemisphere shores; the different paths taken by the individuals and groups who were victims of the Atlantic slave trade were influenced by different factors—including the disembarking region, the ability to be sold on the market, the kind of work performed, gender, age, religion, and language.

Patrick Manning estimates that about 12 million slaves entered the Atlantic trade between the 16th and 19th centuries, but about 1.5 million died on board ship. About 10.5 million slaves arrived in the Americas. Besides the slaves who died on the Middle Passage, more Africans likely died during the slave raids and wars in Africa and forced marches to ports. Manning estimates that 4 million died inside Africa after capture, and many more died young. Manning's estimate covers the 12 million who were originally destined for the Atlantic, as well as the 6 million destined for Arabian slave markets and the 8 million destined for African markets. Of the slaves shipped to the Americas, the largest share went to Brazil and the Caribbean.

Canadian scholar Adam Jones characterized the deaths of millions of Africans during the Atlantic slave trade as genocide. He called it "one of the worst holocausts in human history", and claims arguments to the contrary such as "it was in slave owners' interest to keep slaves alive, not exterminate them" to be "mostly sophistry" stating: "the killing and destruction were intentional, whatever the incentives to preserve survivors of the Atlantic passage for labour exploitation. To revisit the issue of intent already touched on: If an institution is deliberately maintained and expanded by discernible agents, though all are aware of the hecatombs of casualties it is inflicting on a definable human group, then why should this not qualify as genocide?"

Saidiya Hartman has argued that the deaths of enslaved people was incidental to the acquisition of profit and to the rise of capitalism: "Death wasn't a goal of its own but just a by-product of commerce, which has the lasting effect of making negligible all the millions of lives lost. Incidental death occurs when life has no normative value, when no humans are involved, when the population is, in effect, seen as already dead." Hartman highlights how the Atlantic slave trade created millions of corpses but, unlike the concentration camp or the gulag, extermination was not the final objective; it was a corollary to the making of commodities.

Most of the Atlantic slave trade was carried out by seven nations and most of the slaves were carried to their own colonies in the new world. But there was also significant other trading which is shown in the table below. The records are not complete, and some data is uncertain. The last rows show that there were also smaller numbers of slaves carried to Europe and to other parts of Africa, and at least 1.8 million did not survive the journey and were buried at sea with little ceremony.

Flag of vessels carrying the slaves

Destination	Portuguese	British	French	Spanish	Dutch	American	Danish	Total
Portuguese Brazil	4,821,127	3,804	9,402	1,033	27,702	1,174	130	4,864,372
British Caribbean	7,919	2,208,296	22,920	5,795	6,996	64,836	1,489	2,318,251
French Caribbean	2,562	90,984	1,003,905	725	12,736	6,242	3,062	1,120,216
Spanish Americas	195,482	103,009	92,944	808,851	24,197	54,901	13,527	1,061,524
Dutch Americas	500	32,446	5,189	0	392,022	9,574	4,998	444,729
North America	382	264,910	8,877	1,851	1,212	110,532	983	388,747
Danish West Indies	0	25,594	7,782	277	5,161	2,799	67,385	108,998
Europe	2,636	3,438	664	0	2,004	119	0	8,861
Africa	69,206	841	13,282	66,391	3,210	2,476	162	155,568
did not arrive	748,452	526,121	216,439	176,601	79,096	52,673	19,304	1,818,686
Total	5,848,266	3,259,443	1,381,404	1,061,524	554,336	305,326	111,040	12,521,339

The timeline chart when the different nations transported most of their slaves.

The regions of Africa from which these slaves were taken is given in the following table, from the same source.

Source of slaves, by region

Region	Embarked	Disembarked	did not arrive	% did not arrive
Angola Coast, Loango Coast, and Saint Helena	5,694,570	4,955,430	739,140	12.98%
Bight of Benin	1,999,060	1,724,834	274,226	13.72%
Bight of Biafra	1,594,564	1,317,776	276,788	17.36%
Gold Coast	1,209,322	1,030,917	178,405	14.75%
Senegambia and off-shore Atlantic	755,515	611,017	144,498	19.13%
Southeast Africa and Indian Ocean islands	542,668	436,529	106,139	19.56%
Sierra Leone	388,771	338,783	49,988	12.87%
Windward Coast	336,869	287,366	49,503	14.70%
Total	12,521,339	10,702,652	1,818,687	14.52%

According to Kimani Nehusi, the presence of European slavers affected the way in which the legal code in African societies responded to offenders. Crimes traditionally punishable by some other form of punishment became punishable by enslavement and sale to slave traders. According to David Stannard's American Holocaust, 50% of African deaths occurred in Africa as a result of wars between native kingdoms, which produced the majority of slaves. This includes not only those who died in battles but also those who died as a result of forced marches from inland areas to slave ports on the various coasts. The practice of enslaving enemy combatants and their villages was widespread throughout Western and West Central Africa, although wars were rarely started to procure slaves. The slave trade was largely a by-product of tribal and state warfare as a way of removing potential dissidents after victory or financing future wars. In addition, European nations instigated war between African nations and increased the number of war captives by making alliances with warring nations and shifted trade locations in coastal areas to follow patterns of African military conflicts to acquire more slaves. Some African groups proved particularly adept and brutal at the practice of enslaving, such as Bono State, Oyo, Benin, Igala, Kaabu, Ashanti, Dahomey, the Aro Confederacy and the Imbangala war bands.

In letters written by the Manikongo, Nzinga Mbemba Afonso, to the King João III of Portugal, he writes that Portuguese merchandise flowing in is what is fueling the trade in Africans. He requests the King of Portugal to stop sending merchandise but should only send missionaries. In one of his letters he writes:

Each day the traders are kidnapping our people—children of this country, sons of our nobles and vassals, even people of our own family. This corruption and depravity are so widespread that our land is entirely depopulated. We need in this kingdom only priests and schoolteachers, and no merchandise, unless it is wine and flour for Mass. It is our wish that this Kingdom not be a place for the trade or transport of slaves ... Many of our subjects eagerly lust after Portuguese merchandise that your subjects have brought into our domains. To satisfy this inordinate appetite, they seize many of our black free subjects ... They sell them. After having taken these prisoners [to the coast] secretly or at night ... As soon as the captives are in the hands of white men they are branded with a red-hot iron.

Before the arrival of the Portuguese, slavery had already existed in the Kingdom of Kongo. Afonso I of Kongo believed that the slave trade should be subject to Kongo law. When he suspected the Portuguese of receiving illegally enslaved persons to sell, he wrote to King João III in 1526 imploring him to put a stop to the practice.

The kings of Dahomey sold war captives into transatlantic slavery; they would otherwise have been killed in a ceremony known as the Annual Customs. As one of West Africa's principal slave states, Dahomey became extremely unpopular with neighbouring peoples. Like the Bambara Empire to the east, the Khasso kingdoms depended heavily on the slave trade for their economy. A family's status was indicated by the number of slaves it owned, leading to wars for the sole purpose of taking more captives. This trade led the Khasso into increasing contact with the European settlements of Africa's west coast, particularly the French. Benin grew increasingly rich during the 16th and 17th centuries on the slave trade with Europe; slaves from enemy states of the interior were sold and carried to the Americas in Dutch and Portuguese ships. The Bight of Benin's shore soon came to be known as the "Slave Coast".

King Gezo of Dahomey said in the 1840s:

The slave trade is the ruling principle of my people. It is the source and the glory of their wealth ... the mother lulls the child to sleep with notes of triumph over an enemy reduced to slavery ...

In 1807, the UK Parliament passed the Bill that abolished the trading of slaves. The King of Bonny (now in Nigeria) was horrified at the conclusion of the practice:

We think this trade must go on. That is the verdict of our oracle and the priests. They say that your country, however great, can never stop a trade ordained by God himself.

After being marched to the coast for sale, enslaved people were held in large forts called factories. The amount of time in factories varied, but Milton Meltzer states in Slavery: A World History that around 4.5% of deaths attributed to the transatlantic slave trade occurred during this phase. In other words, over 820,000 people are believed to have died in African ports such as Benguela, Elmina, and Bonny, reducing the number of those shipped to 17.5 million.

After being captured and held in the factories, slaves entered the infamous Middle Passage. Meltzer's research puts this phase of the slave trade's overall mortality at 12.5%. Their deaths were the result of brutal treatment and poor care from the time of their capture and throughout their voyage. Around 2.2 million Africans died during these voyages, where they were packed into tight, unsanitary spaces on ships for months at a time. Measures were taken to stem the onboard mortality rate, such as enforced "dancing" (as exercise) above deck and the practice of force-feeding enslaved persons who tried to starve themselves. The conditions on board also resulted in the spread of fatal diseases. Other fatalities were suicides, slaves who escaped by jumping overboard. The slave traders would try to fit anywhere from 350 to 600 slaves on one ship. Before the African slave trade was completely banned by participating nations in 1853, 15.3 million enslaved people had arrived in the Americas.

Raymond L. Cohn, an economics professor whose research has focused on economic history and international migration, has researched the mortality rates among Africans during the voyages of the Atlantic slave trade. He found that mortality rates decreased over the history of the slave trade, primarily because the length of time necessary for the voyage was declining. "In the eighteenth century many slave voyages took at least 2½ months. In the nineteenth century, 2 months appears to have been the maximum length of the voyage, and many voyages were far shorter. Fewer slaves died in the Middle Passage over time mainly because the passage was shorter."

Despite the vast profits of slavery, the ordinary sailors on slave ships were badly paid and subject to harsh discipline. Mortality of around 20%, a number similar and sometimes greater than those of the slaves, was expected in a ship's crew during the course of a voyage; this was due to disease, flogging, overwork, or slave uprisings. Disease (malaria or yellow fever) was the most common cause of death among sailors. A high crew mortality rate on the return voyage was in the captain's interests as it reduced the number of sailors who had to be paid on reaching the home port.

The slave trade was hated by many sailors, and those who joined the crews of slave ships often did so through coercion or because they could find no other employment.

Meltzer also states that 33% of Africans would have died in the first year at the seasoning camps found throughout the Caribbean. Jamaica held one of the most notorious of these camps. Dysentery was the leading cause of death. Captives who could not be sold were inevitably destroyed. Around 5 million Africans died in these camps, reducing the number of survivors to about 10 million. The purpose of seasoning camps were to obliterate the Africans' identities and culture and prepare them for enslavement. In seasoning camps, enslaved Africans learned a new language and adopted new customs. This process of seasoning slaves took about two or three years.

Over the colony's hundred-year course, about a million slaves succumbed to the conditions of slavery in Haiti. A slave imported into Haiti was expected to die, on average, within 3 years of arrival, and slaves born on the island had a life expectancy of only 15 years.

In the Caribbean, Dutch Guiana, and Brazil, the death rate of enslaved people was high, and the birth rates were low, slaveholders imported more Africans to sustain the slave population. The rate of natural decline in the slave population ran as high as 5 percent a year. While the death rate of enslaved populations in the United States was the same on Jamaican plantations. In the Danish West Indies, and for most of the Caribbean, mortality rate was high because of the taxing labor of sugar cultivation. Sugar was a major cash crop and as the Caribbean plantations exported sugar to Europe and North America, they needed an enslaved work force to make its production economically viable, so slaves were imported from Africa. Enslaved Africans lived in inhumane conditions and the mortality rate of enslaved children under the age of five was forty percent. Many enslaved persons died from smallpox and intestinal worms contracted from contaminated food and water.

The Atlantic slave trade exportation of slaves to Cuba was illegal by 1820; however, Cuba continued to import enslaved Africans from Africa until slavery was abolished in 1886. After the abolition of the slave trade to the United States and British colonies in 1807, Florida imported enslaved Africans from Cuba, many landing in Amelia Island. A clandestine slave ferry operated between Havana, Cuba and Pensacola, Florida. Florida remained under Spanish control until 1821 which made it difficult for the United States to cease the smuggling of enslaved Africans from Cuba. In 1821, Florida was ceded to the United States and the smuggling of enslaved Africans continued, and from 1821 to 1841 Cuba became a main supplier of enslaved Africans for the United States. Between 1859 and 1862, slave traders made 40 illegal voyages between Cuba and the United States.

The costs of the shipment of human cargo from Africa and operating costs of the slave trade from Africa into Cuba rose in the mid-19th century. Historian Laird Bergad writes of the Cuban slave trade and slave prices: "...slave prices on the African coast seem to have remained remarkably stable from the 1840s through the mid-1860s, although shipping and operating costs for slave traders seem to have risen considerably. In addition, increased bribes to Spanish colonial officials effectively raised operating costs for slavers. These factors did not restrict the number of Africans embarking for Cuba, nor can they be used alone to explain Cuban slave price rises in the late 1850s and early 1860s. Three interacting factors produced the overwhelming demand for slaves responsible for pushing prices to the high levels[...] The first was the uncertainty surrounding the future of the slave trade itself. The long and persistent British campaign to force an end to the Cuban trade had traditionally been circumvented by collusion between Spanish colonial officials and Cuban slave traders. An additional obstacle to British efforts was the unwillingness of the United States to permit the search of U.S.-flag vessels suspected of involvement in the slave trade". By the mid-1860s, prices of Africans in their elderly years decreased while prices of younger Africans increased because they were considered to be of prime working age. According to research, in 1860 in Matanzas, about 39.6 percent of slaves sold were young prime aged Africans of either sex; in 1870 the percentage was 74.3 percent. In addition, as the cost of sugar increased so did the price of slaves.

The life expectancy for Brazil's slave plantation's for African descended slaves was around 23 years. The trans-Atlantic slave trade into Brazil was outlawed in 1831. To replace the demand for slaves, slaveholders in Brazil turned to slave reproduction. Enslaved women were forced to give birth to eight or more enslaved children. Some slaveholders promised enslaved women their freedom if they gave birth to eight children. In 1873 in the village of Santa Ana, province of Ceará an enslaved woman named Macária was promised her freedom after she gave birth to eight children. An enslaved woman Delfina killed her baby because she did not want her enslaver Manoel Bento da Costa to own her baby and enslave her child. Brazil practiced partus sequitur ventrem to increase the slave population through enslaved female reproduction, because in the 19th century, Brazil needed a large enslaved labor force to work on the sugar plantations in Bahia and the agricultural and mining industries of Minas Gerais, São Paulo, and Rio de Janeiro. After the abolition of the Atlantic slave trade to Brazil, the inter-provincial trade increased which slaveholders forced and depended on enslaved women to give birth to as many children as possible to supply the demand for slaves. Abolitionists in Brazil wanted to abolish slavery by removing partus sequitur ventrem because it was used to perpetuate slavery. For example, historian Martha Santos writes of the slave trade, female reproduction, and abolition in Brazil: "A proposal centered on the 'emancipation of the womb', authored by the influential jurist and politician Agostinho Marques Perdigão Malheiro, was officially endorsed by Pedro II as the most practical means to end slavery in a controlled and peaceful manner. This conservative proposal, a modified version of which became the 'free womb' law passed by Parliament in 1871, did provide for the freedom of children subsequently born of enslaved women, while it forced those children to serve their mothers' masters until age twenty-one, and deferred complete emancipation to a later date".

The birth rate was more than 80 percent higher in the United States because of a natural growth in the slave population and slave breeding farms. Birth rates were low for the first generation of slaves imported from Africa, but, in the US, may have increased in the 19th century to some 55 per thousand, approaching the biological maximum for human populations.

After the prohibition of the trans-atlantic slave trade in 1807, slaveholders in the Deep South of the United States needed more slaves to work in the cotton and sugar fields. To fill the demand for more slaves, slave breeding was practiced in Richmond, Virginia. Richmond sold thousands of enslaved people to slaveholders in the Deep South to work the cotton, rice, and sugar plantations. Virginia was known as a "breeder state." A slaveholder in Virginia bragged his slaves produced 6,000 enslaved children for sale. About 300,000 to 350,000 enslaved people were sold from Richmond's slave breeding farms. Slave breeding farms and forced reproduction on enslaved young girls and women caused reproductive health issues. Enslaved women found ways to resist forced reproduction by causing miscarriages and abortions by taking plants and medicines. Slaveholders tried to control enslaved women's reproduction by encouraging them to have relationships with enslaved men. "Some slaveholders took matters into their own hands, however, and paired enslaved men and women together with the intent that they would procreate." Enslaved teenage girls gave birth at the ages of fifteen or sixteen years old. Enslaved women gave birth in their early twenties. To meet the demands of slaveholders' needs to birth more slaves, enslaved girls and women had seven or nine children. Enslaved girls and women were forced to give birth to as many slaves as possible. The mortality rate of enslaved mothers and children was high because of poor nutrition, sanitation, lack of medical care, and overwork. In the United States a slave's life expectancy was 21 to 22 years, and a black child through the age of 1 to 14 had twice the risk of dying of a white child of the same age.

Slave breeding replaced the demand for enslaved laborers after the decline of the Atlantic slave trade to the United States which caused an increase in the domestic slave trade. The sailing of slaves in the domestic slave trade is known as "sold down the river," indicating slaves being sold from Louisville, Kentucky which was a slave trading city and supplier of slaves. Louisville, Kentucky, Virginia, and other states in the Upper South supplied slaves to the Deep South carried on boats going down the Mississippi River to Southern slave markets. New Orleans, Louisiana became a major slave market in the United States domestic slave trade after the prohibition of the Atlantic slave trade in 1807. Between 1819 and 1860, 71,000 enslaved people were transported to New Orlean's slave market on slave ships that departed from ports in the United States along the Atlantic and Gulf of Mexico to New Orleans to supply the demand for slaves in the Deep South.

Texas participated in the illegal slave trade and imported enslaved persons from Cuba to Galveston Island which was the main illegal slave port in Texas. Texas was part of Mexico from 1821 until 1836, and Cuba continued to supply African slaves to many Latin American countries. After 1821, the smuggling of slaves into Texas increased because of slaveholders' demand for additional enslaved labor. Galveston Island is located in the Gulf of Mexico and is 800 miles away from the slave ports in Cuba and between 60 and 70 miles away from the Louisiana border. Smugglers utilized these geographic locations to their advantage and illegally imported enslaved Africans from Cuba and made a profit by selling Africans to slaveholders in Texas and Louisiana. For example, French pirate and privateer Jean Lafitte, established a colony on Galveston Island in 1817 and participated in privateering for four years and made a profit by smuggling in slaves and sold over 200 Africans to slaveholders in the United States. Lafitte used intermediaries such as the Bowie brothers, John, Resin, and James who contracted with slave traders and planters from the United States who had an interest in buying slaves. From 1818 to 1820, Lafitte and the Bowie brothers made $65,000 smuggling Africans into the Southern states and selling them to planters in Louisiana and Mississippi.

Historian Ernest Obadele-Starks estimated that after 1807 the number of enslaved Africans smuggled into the United States annually averaged as low as 3,500. New Orleans, Louisiana and Florida were centers for the illegal importation of slaves in the United States because of their close proximity to Cuba and the other Caribbean islands that provided Southern states enslaved labor.

Many diseases, each capable of killing a large minority or even a majority of a new human population, arrived in the Americas after 1492. They include smallpox, malaria, bubonic plague, typhus, influenza, measles, diphtheria, yellow fever, and whooping cough. During the Atlantic slave trade following the discovery of the New World, diseases such as these are recorded as causing mass mortality. Due to the many diseases in the African continent, Europeans nicknamed Sierra Leone in West Africa "white man's grave" because of the number of European deaths from diseases. From 1819 to 1836, the regions of Africa that had the highest European deaths from malaria were Sierra Leone and Senegal. Out of European deaths per 1,000, 164.66 whites died from malaria in Senegal, and 483 whites died from malaria in Sierra Leone. Sierra Leone had the highest number of whites dying from malaria accounting for 40 percent of deaths each year, because of this it was nicknamed "white man's grave." The phrase white man's grave was coined in the 1830s. However, Europeans prior to the creation of the phrase considered Africa a dangerous environment due to tropical heat and the high death rates of people dying from diseases, which was why the phrase was created in the 19th century.

Malaria thrives in warm and humid climates. In North America malaria did not spread as much because certain climatic regions were not conducive to the disease's survival. European American slaveholders preferred Africans who had immunity to malaria be trafficked to the slave ports. The price of Africans born in regions where malaria was dominate were higher. Historian Elena Esposito explains: "By looking at the historical prices of African slaves in the United States, we find evidence of a malaria premium granted by resistance to the disease. In fact, we show that on Louisiana plantations, more malaria resistant individuals - those born in regions of Africa with a higher prevalence of malaria - commanded significantly higher prices."

Evolutionary history may also have played a role in African people's resistance to diseases in the contitent, and Indigenous peoples/Native Americans lack of resistance to African borne diseases. Compared to Africans and Europeans, New World populations did not have a history of exposure to diseases such as malaria, and therefore, no genetic resistance had been produced as a result of adaptation through natural selection.

Levels and extent of immunity varies from disease to disease. For smallpox and measles for example, those who survive are equipped with the immunity to combat the disease for the rest of their life in that they cannot contract the disease again. There are also diseases, such as malaria, which do not confer effective lasting immunity.

Epidemics of smallpox were known for causing a significant decrease in the Indigenous population of the New World. The effects on survivors included pockmarks on the skin which left deep scars, commonly causing significant disfigurement. Some Europeans, who believed the plague of syphilis in Europe to have come from the Americas, saw smallpox as the European revenge against the Natives. Africans and Europeans, unlike the native population, often had lifelong immunity, because they had often been exposed to minor forms of the illness such as cowpox or variola minor disease in childhood. By the late 16th century, there existed some forms of inoculation and variolation in Africa and the Middle East. One practice features Arab traders in Africa "buying-off" the disease in which a cloth that had been previously exposed to the sickness was to be tied to another child's arm to increase immunity. Another practice involved taking pus from a smallpox scab and putting it in the cut of a healthy individual in an attempt to have a mild case of the disease in the future rather than the effects becoming fatal.

The trade of enslaved Africans in the Atlantic has its origins in the explorations of Portuguese mariners down the coast of West Africa in the 15th century. Before that, contact with African slave markets was made to ransom Portuguese who had been captured by the intense North African Barbary pirate attacks on Portuguese ships and coastal villages, frequently leaving them depopulated. The first Europeans to use enslaved Africans in the New World were the Spaniards, who sought auxiliaries for their conquest expeditions and labourers on islands such as Cuba and Hispaniola. The alarming decline in the native population had spurred the first royal laws protecting them (Laws of Burgos, 1512–13). The first enslaved Africans arrived in Hispaniola in 1501. After Portugal had succeeded in establishing sugar plantations (engenhos) in northern Brazil c. 1545, Portuguese merchants on the West African coast began to supply enslaved Africans to the sugar planters. While at first these planters had relied almost exclusively on the native Tupani for slave labour, after 1570 they began importing Africans, as a series of epidemics had decimated the already destabilized Tupani communities. By 1630, Africans had replaced the Tupani as the largest contingent of labour on Brazilian sugar plantations. This ended the European medieval household tradition of slavery, resulted in Brazil's receiving the most enslaved Africans, and revealed sugar cultivation and processing as the reason that roughly 84% of these Africans were shipped to the New World.

On November 7, 1693, Charles II issued a royal decree, providing sanctuary in Spanish Florida for fugitive slaves from the British colony of South Carolina.

As Britain rose in naval power and settled continental North America and some islands of the West Indies, they became the leading slave traders. At one stage the trade was the monopoly of the Royal African Company, operating out of London. But, following the loss of the company's monopoly in 1689, Bristol and Liverpool merchants became increasingly involved in the trade. By the late 18th century, one out of every four ships that left Liverpool harbour was a slave trading ship. Much of the wealth on which the city of Manchester, and surrounding towns, was built in the late 18th century, and for much of the 19th century, was based on the processing of slave-picked cotton and manufacture of cloth. Other British cities also profited from the slave trade. Birmingham, the largest gun-producing town in Britain at the time, supplied guns to be traded for slaves. 75% of all sugar produced in the plantations was sent to London, and much of it was consumed in the highly lucrative coffee houses there.

The first slaves to arrive as part of a labour force in the New World reached the island of Hispaniola (now Haiti and the Dominican Republic) in 1502. Cuba received its first four slaves in 1513. Jamaica received its first shipment of 4,000 slaves in 1518. "Between the 1490s and the 1850s, Latin America, including the Spanish-speaking Caribbean and Brazil, imported the largest number of African slaves to the New World, generating the single-greatest concentration of black populations outside of the African continent." About 4 million enslaved Africans were transported to the Caribbean by way of the transatlantic slave trade. Cuba, the largest slave colony in Hispanic America, imported 800,000 enslaved Africans and participated in the illegal slave trade longer than any other. Enslaved Africans worked about 16 hours a day on the sugarcane plantations. They brought their traditional religions from West Africa; these developed in the new world as religions that scholars call African diaspora religions.

Slave exports to Honduras and Guatemala started in 1526. Historian Nigel Bolland writes of the slave trade in Central America: "The demand for labor in the early Spanish settlements of Hispaniola, Cuba, Panama, and Peru resulted in a large-scale Indian (Indigenous people) slave trade in Central America in the second quarter of the 16th century. Indeed, the first colonial economy of the region was based on slave trading."

In the 16th century, the majority of Africans imported to Central America came from present-day Senegambia and other West African regions. Between 1607 and 1640, Portuguese slave traders imported Africans from Angola to Honduras and were sold in Santiago de Guatemala to work in the sugar and indigo plantations. The majority of the Africans working in the plantations were from the Luanda region in Central Africa.

The first enslaved Africans to reach what would become the United States arrived in July 1526 as part of a Spanish attempt to colonize San Miguel de Gualdape. By November, the 300 Spanish colonists were reduced to 100, and their slaves from 100 to 70. The enslaved people revolted in 1526 and joined a nearby Native American tribe, while the Spanish abandoned the colony altogether (1527). The area of the future Colombia received its first enslaved people in 1533. El Salvador, Costa Rica, and Florida began their stints in the slave trade in 1541, 1563, and 1581, respectively. According to research, about 40 percent of enslaved Africans arrived at Gadsden's Wharf, which was the largest slave port in the United States. In the 17th century in colonial Boston in Massachusetts, about 166 transatlantic voyages embarked out of Boston. Boston imported enslaved people from Africa and exported rum. Peter Faneuil organized and profited from the trans-Atlantic voyages out of Boston and imported manufactured goods from Europe, and imported enslaved people, rum, and sugar from the Caribbean. Connecticut, Massachusetts, and Rhode Island were the three New England states with the largest slave populations. The enslaved population in South Kingston, Rhode Island was thirty percent, in Boston the slave population was ten percent, in New London it was nine percent, and in New York it was 7.2 percent. The earliest documentation of enslaved people in New England was 1638. In Northern American British colonies, Massachusetts Bay colonies was the center for slave trading and colonial Boston was a major slave port in the North importing slaves directly from Africa.

The 17th century saw an increase in shipments. Africans were brought to Point Comfort – several miles downriver from the English colony of Jamestown, Virginia – in 1619. The first kidnapped Africans in English North America were classed as indentured servants and freed after seven years. Virginia law codified chattel slavery in 1656, and in 1662 the colony adopted the principle of partus sequitur ventrem, which classified children of slave mothers as slaves, regardless of paternity. Under British law, children born of white male slave owners and black female slaves would have inherited the father's status and rights. The change to maternal inheritance for slaves guaranteed that anyone born with any slave ancestors was a slave, with no regard to the nature of the relations between the white father and the black mother, consensual or not.

In addition to African persons, Indigenous peoples of the Americas were trafficked through Atlantic trade routes. The 1677 work The Doings and Sufferings of the Christian Indians, for example, documents English colonial prisoners of war (not, in fact, opposing combatants, but imprisoned members of English-allied forces) being enslaved and sent to Caribbean destinations. Captive Indigenous opponents, including women and children, were also sold into slavery at a substantial profit, to be transported to West Indies colonies.

The Spanish and Portuguese colonized South America and enslaved the Indigenous people. They later enslaved Africans brought from West and Central Africa in ships by way of the Atlantic slave trade. Brazil imported 4.8 million enslaved Africans. Africans who escaped slavery there formed quilombos, maroon communities with degrees of self-governance. Palamares, a quilombo community, lasted for 100 years while other communities were quickly removed by the Dutch and Portuguese. The Africans imported to Brazil were Yoruba, Fon, Bantu and others. Their religions from Africa developed into new world religions in Brazil called Candomblé, Umbanda, Xango, and Macumba.

Historian Erika Edwards writes of the slave trade in Argentina: "In 1587 the first slaves arrived in Buenos Aires from Brazil. From 1580 to 1640, the main commercial activity for Buenos Aires was the slave trade. More than 70 percent of the value of all imports arriving in Buenos Aires were enslaved Africans. Slaves came primarily from Brazil via the Portuguese slave trade from Angola and other western states in Africa. Once arriving in Buenos Aires, they could be sent as far as Lima, Peru; slaves were provided to Mendoza, Tucuman, and Salta Jujuy as well as to Chile, Paraguay, and what is today Bolivia and southern Peru."

By 1802, Russian colonists noted that "Boston" (U.S.-based) skippers were trading African slaves for otter pelts with the Tlingit people in Southeast Alaska.

Distribution of slaves (1519–1867)

Destination	Percent
Portuguese America	38.5%
British West Indies	18.4%
Spanish Empire	17.5%
French West Indies	13.6%
English/British North America / United States	9.7%
Dutch West Indies	2.0%
Danish West Indies	0.3%

Notes:

• Before 1820, the number of enslaved Africans transported across the Atlantic to the New World was triple the number of Europeans who reached North and South American shores. At the time this was the largest oceanic displacement or migration in history, eclipsing even the far-flung, but less-dense, expansion of Austronesian-Polynesian explorers.
• The number of Africans who arrived in each region is calculated from the total number of slaves imported, about 10,000,000.
• Includes British Guiana and British Honduras

• 
  Punishing slaves at Calabouco, in Rio de Janeiro, c. 1822
• 
  Recently bought slaves in Brazil on their way to the farms of the landowners who bought them c. 1830
• 
  A 19th-century lithograph showing a sugarcane plantation in Suriname

In 18th-century France, returns for investors in plantations averaged around 6%; as compared to 5% for most domestic alternatives, this represented a 20% profit advantage. Risks—maritime and commercial—were important for individual voyages. Investors mitigated it by buying small shares of many ships at the same time. In that way, they were able to diversify a large part of the risk away. Between voyages, ship shares could be freely sold and bought.

By far the most financially profitable West Indian colonies in 1800 belonged to the United Kingdom. After entering the sugar colony business late, British naval supremacy and control over key islands such as Jamaica, Trinidad, the Leeward Islands, and Barbados and the territory of British Guiana gave it an important edge over all competitors; while many British did not make gains, a handful of individuals made small fortunes. This advantage was reinforced when France lost its most important colony, St. Domingue (western Hispaniola, now Haiti), to a slave revolt in 1791 and supported revolts against its rival Britain, in the name of liberty after the 1793 French revolution. Before 1791, British sugar had to be protected to compete against cheaper French sugar.

After 1791, the British islands produced the most sugar, and the British people quickly became the largest consumers. West Indian sugar became ubiquitous as an additive to Indian tea. It has been estimated that the profits of the slave trade and of West Indian plantations created up to one-in-twenty of every pound circulating in the British economy at the time of the Industrial Revolution in the latter half of the 18th century.

Following the Slavery Abolition Act 1833 which gradually abolished slavery in the British Empire, the UK government took out a loan of £15 million ($4.25 billion in 2023) to compensate former slave owners for the loss of their "property" after their slaves were freed. Compensation was not given to the formerly enslaved people.

Historian Walter Rodney has argued that at the start of the slave trade in the 16th century, although there was a technological gap between Europe and Africa, it was not very substantial. Both continents were using Iron Age technology. The major advantage that Europe had was in ship building. During the period of slavery, the populations of Europe and the Americas grew exponentially, while the population of Africa remained stagnant. Rodney contended that the profits from slavery were used to fund economic growth and technological advancement in Europe and the Americas. Based on earlier theories by Eric Williams, he asserted that the industrial revolution was at least in part funded by agricultural profits from the Americas. He cited examples such as the invention of the steam engine by James Watt, which was funded by plantation owners from the Caribbean.

Other historians have attacked both Rodney's methodology and accuracy. Joseph C. Miller has argued that the social change and demographic stagnation (which he researched on the example of West Central Africa) was caused primarily by domestic factors. Joseph Inikori provided a new line of argument, estimating counterfactual demographic developments in case the Atlantic slave trade had not existed. Patrick Manning has shown that the slave trade did have a profound impact on African demographics and social institutions, but criticized Inikori's approach for not taking other factors (such as famine and drought) into account, and thus being highly speculative.

The effect of the trade on African societies is much debated, due to the influx of goods to Africans. Proponents of the slave trade, such as Archibald Dalzel, argued that African societies were robust and not much affected by the trade. In the 19th century, European abolitionists, most prominently David Livingstone, took the opposite view, arguing that the fragile local economy and societies were being severely harmed by the trade. According to research from historian Nathan Nunn, the underdeveloped infrastructure and economy in Africa is a result of colonization and the slave trade. Nunn wrote: "...Africa's poor economic performance is a result of postcolonial state failure, the roots of which lie in the underdevelopment and instability of precolonial polities..., because of a lack of significant political development during colonial rule, the limited precolonial political structures continued to exist after independence. As a result, Africa's postindependence leaders inherited nation states that did not have the infrastructure necessary to extend authority and control over the whole country. Many states were, and still are, unable to collect taxes from their citizens, and as a result they are also unable to provide a minimum level of public goods and services".

Some African rulers saw an economic benefit from trading their subjects with European slave traders. With the exception of Portuguese-controlled Angola, coastal African leaders "generally controlled access to their coasts, and were able to prevent direct enslavement of their subjects and citizens". Thus, as African scholar John Thornton argues, African leaders who allowed the continuation of the slave trade likely derived an economic benefit from selling their subjects to Europeans. The Kingdom of Benin, for instance, participated in the African slave trade, at will, from 1715 to 1735, surprising Dutch traders, who had not expected to buy slaves in Benin. The benefit derived from trading slaves for European goods was enough to make the Kingdom of Benin rejoin the trans-Atlantic slave trade after centuries of non-participation. Such benefits included military technology (specifically guns and gunpowder), gold, or simply maintaining amicable trade relationships with European nations. The slave trade was, therefore, a means for some African elites to gain economic advantages. Historian Walter Rodney estimates that by c. 1770, the King of Dahomey was earning an estimated £250,000 per year by selling captive African soldiers and enslaved people to the European slave-traders. Many West African countries also already had a tradition of holding slaves, which was expanded into trade with Europeans.

The Atlantic trade brought new crops to Africa and more efficient currencies which were adopted by the West African merchants. This can be interpreted as an institutional reform which reduced the cost of doing business. But the developmental benefits were limited as long as the business including slaving.

Both Thornton and Fage contend that while African political elite may have ultimately benefited from the slave trade, their decision to participate may have been influenced more by what they could lose by not participating. In Fage's article "Slavery and the Slave Trade in the Context of West African History", he notes that for West Africans "... there were really few effective means of mobilizing labour for the economic and political needs of the state" without the slave trade.

Historian Eric Williams in 1994 argued that the profits that Britain received from its sugar colonies, or from the slave trade between Africa and the Caribbean, contributed to the financing of Britain's industrial revolution. However, he says that by the time of the abolition of the slave trade in 1807, and the emancipation of the slaves in 1833, the sugar plantations of the British West Indies had lost their profitability, and it was in Britain's economic interest to emancipate the slaves.

Other researchers and historians have strongly contested what has come to be referred to as the "Williams thesis" in academia. David Richardson has concluded that the profits from the slave trade amounted to less than 1% of domestic investment in Britain. Economic historian Stanley Engerman finds that even without subtracting the associated costs of the slave trade (e.g., shipping costs, slave mortality, mortality of British people in Africa, defense costs) or reinvestment of profits back into the slave trade, the total profits from the slave trade and of West Indian plantations amounted to less than 5% of the British economy during any year of the Industrial Revolution. Engerman's 5% figure gives as much as possible in terms of benefit of the doubt to the Williams argument, not solely because it does not take into account the associated costs of the slave trade to Britain, but also because it carries the full-employment assumption from economics and holds the gross value of slave trade profits as a direct contribution to Britain's national income. Historian Richard Pares, in an article written before Williams' book, dismisses the influence of wealth generated from the West Indian plantations upon the financing of the Industrial Revolution, stating that whatever substantial flow of investment from West Indian profits into industry there occurred after emancipation, not before. However, each of these works focus primarily on the slave trade or the Industrial Revolution, and not the main body of the Williams thesis, which was on sugar and slavery itself. Therefore, they do not refute the main body of the Williams thesis.

Seymour Drescher and Robert Anstey argue the slave trade remained profitable until the end, and that moralistic reform, not economic incentive, was primarily responsible for abolition. They say slavery remained profitable in the 1830s because of innovations in agriculture. However, Drescher's Econocide wraps up its study in 1823, and does not address the majority of the Williams thesis, which covers the decline of the sugar plantations after 1823, the emancipation of the slaves in the 1830s, and the subsequent abolition of sugar duties in the 1840s. These arguments do not refute the main body of the Williams thesis, which presents economic data to show that the slave trade was minor compared to the wealth generated by sugar and slavery itself in the British Caribbean.

Karl Marx, in his influential economic history of capitalism, Das Kapital, wrote that "... the turning of Africa into a warren for the commercial hunting of black-skins, signaled the rosy dawn of the era of capitalist production". He argued that the slave trade was part of what he termed the "primitive accumulation" of capital, the 'non-capitalist' accumulation of wealth that preceded and created the financial conditions for Britain's industrialisation.

The demographic effects of the slave trade is a controversial and highly debated issue. Although scholars such as Paul Adams and Erick D. Langer have estimated that sub-Saharan Africa represented about 18 percent of the world's population in 1600 and only 6 percent in 1900, the reasons for this demographic shift have been the subject of much debate. In addition to the depopulation Africa experienced because of the slave trade, African nations were left with severely imbalanced gender ratios, with females comprising up to 65 percent of the population in hard-hit areas such as Angola. Moreover, many scholars (such as Barbara N. Ramusack) have suggested a link between the prevalence of prostitution in Africa today with the temporary marriages that were enforced during the course of the slave trade.

Walter Rodney argued that the export of so many people had been a demographic disaster which left Africa permanently disadvantaged when compared to other parts of the world, and it largely explains the continent's continued poverty. He presented numbers showing that Africa's population stagnated during this period, while those of Europe and Asia grew dramatically. According to Rodney, all other areas of the economy were disrupted by the slave trade as the top merchants abandoned traditional industries in order to pursue slaving, and the lower levels of the population were disrupted by the slaving itself.

Others have challenged this view. J. D. Fage compared the demographic effect on the continent as a whole. David Eltis has compared the numbers to the rate of emigration from Europe during this period. In the 19th century alone over 50 million people left Europe for the Americas, a far higher rate than were ever taken from Africa.

Other scholars accused Walter Rodney of mischaracterizing the trade between Africans and Europeans. They argue that Africans, or more accurately African elites, deliberately let European traders join in an already large trade in enslaved people and that they were not patronized.

As Joseph E. Inikori argues, the history of the region shows that the effects were still quite deleterious. He argues that the African economic model of the period was very different from the European model, and could not sustain such population losses. Population reductions in certain areas also led to widespread problems. Inikori also notes that after the suppression of the slave trade Africa's population almost immediately began to rapidly increase, even prior to the introduction of modern medicines.

The cultural effects of the transatlantic slave trade in Africa are the reduction of traditional African religious practices. According to research in a 2021 census of religions practiced in Ghana published by the Office of International Religious Freedom, in 2021 the Ghana Embassy reported "71 percent of the population are Christian, 20 percent Muslim, 3 percent adhere to indigenous or animistic religious beliefs, and 6 percent belong to other religious groups or have no religious beliefs". Historian Nana Osei Bonsu argued that the transatlantic slave trade not only took millions of Africans from the continent but also caused a decline of traditional African religions and Ghanaian indigenous culture as Europeans believed African people's culture and religions were irrelevant and inferior. The slave trade resulted in the colonization of Africa and its people forcing many Africans to convert to Christianity.

The transatlantic slave trade affected traditional trade routes in West-Central Africa. Africans traded goods and slaves using trade routes in the interior of Africa that connected to the Sahara Desert and the Mediterranean coast where other commodities and enslaved people were traded. These trade routes were used by Africans for centuries and societies and kingdoms developed as a result. Europeans chose to trade primarily along the Atlantic coast because they did not have immunity to malaria that was endemic to the region and "they could not dominate further than their guns could fire, from ship or fort". The slave trade also left warlords in charge in African societies as they wanted to trade with Europeans to obtain guns to defeat their enemies and sell them to Europeans. The European system of monetization implemented with the slave trade replaced cowrie shells, the currency traditionally used among Africans. According to research from the National Park Service: "European trade goods supplanted former African reliance on indigenous material goods, natural resources and products as the economic basis of their society. At the same time Europeans increasingly required people in exchange for trade goods. Once this stage was reached an African society had little choice but to trade human lives for European goods and guns; guns that had become necessary to wage wars for further captives in order to trade for goods upon which an African society was now dependent".

As the European slave trade grew more profitable, the demand for slaves increased, which affected African coastal societies in the following ways: "Commerce with the world outside Africa changed from overland to sea and coastal villages whose main trades had been fishing and salt production became ports and trading posts". The trans-Atlantic slave trade resulted in the colonization of Africa. Colonization in Africa continues to have negative effects as some traditional African cultures are erased, along with traditional languages and traditional African religions. After the trans-Atlantic slave trade had ceased, European colonial powers fought over the land and resources in Africa. The development of the antimalarial drug quinine in 1820 enabled Europeans to colonize the interior of Africa. By the end of the 19th century, European powers laid claim to 90 percent of land in Sub-Saharan Africa during the "Scramble for Africa". In this invasion and subsequent colonization, the seven European powers (Britain, France, Germany, Belgium, Spain, Portugal, and Italy) removed African kingdoms of power, created national borders that did not align with the already existing ethnic borders in Africa and forced diverse tribal ethnic groups to coexist and be controlled under one colonial power. This caused an unnatural division of people and was the groundwork for the instability in the African continent beginning in the 20th century into the present day.

The slave forts built along the Gold Coast in Ghana during the years of the slave trade were owned and used by the British colonial administration as their headquarters well into the 20th century. British forts in Ghana were vacated after Ghana gained independence in 1957. The placement of these forts dislocated African societies that lived and fished along the coast. British colonists used the fort to imprison African resistance leaders who organized resistance movements against colonization. In 1900, Yaa Asantewaa (Queen mother and war leader of the Ashanti people), was imprisoned at Elmina Castle because she led a war against the British for possession of the Golden Stool, or Ashanti royal throne.

Walter Rodney states:

The role of slavery in promoting racist prejudice and ideology has been carefully studied in certain situations, especially in the USA. The simple fact is that no people can enslave another for four centuries without coming out with a notion of superiority, and when the colour and other physical traits of those peoples were quite different it was inevitable that the prejudice should take a racist form.

Eric Williams argued that "A racial twist [was] given to what is basically an economic phenomenon. Slavery was not born of racism: rather, racism was the consequence of slavery."

Similarly, John Darwin writes, "The rapid conversion from white indentured labour to black slavery ... made the English Caribbean a frontier of civility where English (later British) ideas about race and slave labour were ruthlessly adapted to local self-interest.... Indeed, the root justification for the system of slavery and the savage apparatus of coercion on which its preservation depended was the ineradicable barbarism of the slave population, a product, it was argued, of its African origins".

Although slavery was practiced in ancient times in various cultures, it did not have a global effect like the transatlantic slave trade and slavery in the Americas created by Europeans. The transatlantic slave trade's legacy is institutional racism on an international scale that led to racial discrimination in educational institutions and public places. In addition, scientific racism was taught in schools and some colleges in the United States and Europe in the 19th century and early 20th centuries that was used as a justification to enslave Africans. The Canadian Museum for Human Rights explained how European slavery differed from the slavery practiced by Africans and Native Americans. "Europeans brought a different kind of slavery to North America, however. Many Europeans saw enslaved people merely as property to be bought and sold. This 'chattel slavery' was a dehumanizing and violent system of abuse and subjugation. Importantly, Europeans viewed slavery in racist terms. Indigenous and African peoples were seen as less than human. This white supremacy justified the violence of slavery for hundreds of years." Another example from an article from The Wall Street Journal explained, "New World slavery was a racialized institution in which slaves were black and slave owners were white. In contrast, owners and slaves in the Old World were generally of the same race. Distinctions between enslaved and freeborn people were often framed not in racial terms but in terms of language, culture and religion." Scientific racism and the history of enslaving sub-Saharan Africans led to anti-black racism that is seen worldwide.

In Britain, America, Portugal, and in parts of Europe, opposition developed against the slave trade. David Brion Davis says that abolitionists assumed "that an end to slave imports would lead automatically to the amelioration and gradual abolition of slavery". In Britain and America, opposition to the trade was led by members of the Religious Society of Friends (Quakers), Thomas Clarkson and establishment Evangelicals such as William Wilberforce in Parliament. Many people joined the movement and they began to protest against the trade, but they were opposed by the owners of the colonial holdings. Following Lord Mansfield's decision in 1772, many abolitionists and slave-holders believed that slaves became free upon entering the British isles. However, in reality occasional instances of slavery continued in Britain right up to abolition in the 1830s. The Mansfield ruling on Somerset v Stewart only decreed that a slave could not be transported out of England against his will.

Under the leadership of Thomas Jefferson, the new U.S. state of Virginia in 1778 became the first slave-owning state and one of the first jurisdictions anywhere to stop the importation of new slaves for sale; it made it a crime for traders to bring in slaves from out of state or from overseas for sale; migrants from within the United States were allowed to bring their own slaves. The new law freed all slaves brought in illegally after its passage and imposed heavy fines on violators. All the other states in the United States followed suit, although South Carolina reopened its slave trade in 1803.

Denmark, which had been active in the slave trade, was the first country to ban the trade through legislation in 1792, which took effect in 1803. Britain banned the slave trade in 1807, imposing stiff fines for any slave found aboard a British ship (see Slave Trade Act 1807). The Royal Navy moved to stop other nations from continuing the slave trade and declared that slaving was equal to piracy and was punishable by death. The United States Congress passed the Slave Trade Act of 1794, which prohibited the building or outfitting of ships in the U.S. for use in the slave trade. The U.S. Constitution (Article I, section 9, clause 1) barred a federal prohibition on importing slaves for 20 years; at that time the Act Prohibiting Importation of Slaves prohibited imports on the first day the Constitution permitted: January 1, 1808. It was generally thought that the transatlantic slave trade ended in 1867, but evidence was later found of voyages until 1873.

Quakers began to campaign against the British Empire's slave trade in the 1780s, and from 1789 William Wilberforce was a driving force in the British Parliament in the fight against the trade. The abolitionists argued that the trade was not necessary for the economic success of sugar in the British West Indian colonies. This argument was accepted by wavering politicians, who did not want to destroy the valuable and important sugar colonies of the British Caribbean. Parliament was also concerned about the success of the Haitian Revolution, and they believed they had to abolish the trade to prevent a similar conflagration from occurring in a British Caribbean colony.

On 22 February 1807, the House of Commons passed a motion by 283 votes to 16 to abolish the Atlantic slave trade. Hence, the slave trade was abolished, but not the still-economically viable institution of slavery itself, which provided Britain's most lucrative import at the time, sugar. Abolitionists did not move against sugar and slavery itself until after the sugar industry went into terminal decline after 1823.

The United States passed its own Act Prohibiting Importation of Slaves the next week (March 2, 1807), although probably without mutual consultation. The act only took effect on the first day of 1808; since a compromise clause in the US Constitution (Article 1, Section 9, Clause 1) prohibited federal, although not state, restrictions on the slave trade before 1808. The United States did not, however, abolish its internal slave trade, which became the dominant mode of US slave trading until the 1860s. In 1805 the British Order-in-Council had restricted the importation of slaves into colonies that had been captured from France and the Netherlands. Britain continued to press other nations to end its trade; in 1810 an Anglo-Portuguese treaty was signed whereby Portugal agreed to restrict its trade into its colonies; an 1813 Anglo-Swedish treaty whereby Sweden outlawed its slave trade; the Treaty of Paris 1814 where France agreed with Britain that the trade is "repugnant to the principles of natural justice" and agreed to abolish the slave trade in five years; the 1814 Anglo-Dutch treaty where the Dutch outlawed its slave trade.

Abolitionist opinion in Britain was strong enough in 1807 to abolish the slave trade in all British possessions, although slavery itself persisted in the colonies until 1833. Abolitionists after 1807 focused on international agreements to abolish the slave trade. Foreign Minister Castlereagh switched his position and became a strong supporter of the movement. Britain arranged treaties with Portugal, Sweden and Denmark in the period between 1810 and 1814, whereby they agreed to end or restrict their trading. These were preliminary to the Congress of Vienna negotiations that Castlereagh dominated and which resulted in a general declaration condemning the slave trade. The problem was that the treaties and declarations were hard to enforce, given the very high profits available to private interests. As Foreign Minister, Castlereagh cooperated with senior officials to use the Royal Navy to detect and capture slave ships. He used diplomacy to make search-and-seize agreements with all the governments whose ships were trading. There was serious friction with the United States, where the southern slave interest was politically powerful. Washington recoiled at British policing of the high seas. Spain, France and Portugal also relied on the international slave trade to supply their colonial plantations.

As more and more diplomatic arrangements were made by Castlereagh, the owners of slave ships started flying false flags of nations that had not agreed, especially the United States. It was illegal under American law for American ships to engage in the slave trade, but the idea of Britain enforcing American laws was unacceptable to Washington. Lord Palmerston and other British foreign ministers continued the Castlereagh policies. Eventually, in 1842 in 1845, an arrangement was reached between London and Washington. With the arrival of a staunchly anti-slavery government in Washington in 1861, the Atlantic slave trade was doomed. In the long run, Castlereagh's strategy on how to stifle the slave trade proved successful.

Prime Minister Palmerston detested slavery, and in Nigeria in 1851 he took advantage of divisions in native politics, the presence of Christian missionaries, and the maneuvers of British consul John Beecroft to encourage the overthrow of King Kosoko. The new King Akitoye was a docile non-slave-trading puppet.

The Royal Navy's West Africa Squadron, established in 1808, grew by 1850 to a force of some 25 vessels, which were tasked with combating slavery along the African coast. Between 1807 and 1860, the Royal Navy's Squadron seized approximately 1,600 ships involved in the slave trade and freed 150,000 Africans who were aboard these vessels. Several hundred slaves a year were transported by the navy to the British colony of Sierra Leone, where they were made to serve as "apprentices" in the colonial economy until the Slavery Abolition Act 1833.

Even though it was prohibited, in response to the North's reluctance or refusal to enforce the Fugitive Slave Act of 1850, the Atlantic slave trade was "re-open[ed] ... by way of retaliation". In 1859, "the trade in slaves from Africa to the Southern coast of the United States is now carried on in defiance of Federal law and of the Federal Government."

The last known slave ship to land on U.S. soil was the Clotilda, which in 1859 illegally smuggled a number of Africans into the town of Mobile, Alabama. The Africans on board were sold as slaves; however, slavery in the U.S. was abolished five years later following the end of the American Civil War in 1865. Cudjoe Lewis, who died in 1935, was long believed to be the last survivor of Clotilda and the last surviving slave brought from Africa to the United States, but recent research has found that two other survivors from Clotilda outlived him, Redoshi (who died in 1937) and Matilda McCrear (who died in 1940).

However, according to Senator Stephen Douglas, Lincoln's opponent in the Lincoln–Douglas debates:

In regard to the slave trade, Mr. Douglas stated that there was not the shadow of doubt but that it had been carried on quite extensively for a long time back, and that there had been more slaves imported into the Southern States during the last year [1858] than had ever been imported before in any one year, even when the slave trade was legal. It was his confident belief that over 15,000 slaves had been brought into this country during the past year. He had seen, with his own eyes, three hundred of these recently-imported, miserable beings, in a slave-pen in Vicksburg, Mississippi, and also large numbers at Memphis, Tennessee.

Abraham Lincoln faced significant constitutional challenges in his fight to abolish slavery, as the U.S. Constitution had provided protections for slavery. Despite these challenges, Lincoln's leadership and the creation of a strong federal government allowed for the eventual abolition of slavery through the Emancipation Proclamation and the passage of the 13th Amendment.

The last country to ban the Atlantic slave trade was Brazil; a first law was approved in 1831, however it was only enforced in 1850 through the new Eusébio de Queirós Law. Despite the prohibition, it took another three years for the trade to effectively end. Between the first law in 1831 and the effective ban of transatlantic trade in 1850, an estimated 500,000 Africans were enslaved and illegally trafficked to Brazil, and until 1856, the year of the last recorded seizure of a slave ship by the Brazilian authorities, around 38,000 Africans still entered the country as slaves. Historians João José Reis, Sidney Chalhoub, Robert W. Slenes and Flávio dos Santos Gomes proposed that another reason for the abolition of the Atlantic slave trade to Brazil was the Malê Revolt in 1835. On January 25, 1835, an estimated 600 free and enslaved Africans armed with guns ran through the streets of Salvador murdering whites and slaveholders. Abolitionists argued that if the slave trade and slavery continued, slave resistance movements would increase, resulting in more deaths. Seventy three percent of the Africans in the Malê revolt were Yoruba men who converted to Islam; some white Brazilians believed they had a spirit of resistance against enslavement.

The historian Walter Rodney contends that it was a decline in the profitability of the triangular trades that made it possible for certain basic human sentiments to be asserted at the decision-making level in a number of European countries—Britain being the most crucial because it was the greatest carrier of African captives across the Atlantic. Rodney states that changes in productivity, technology, and patterns of exchange in Europe and the Americas informed the decision by the British to end their participation in the trade in 1807.

Nevertheless, Michael Hardt and Antonio Negri argue that it was neither a strictly economic nor a moral matter. First, because slavery was (in practice) still beneficial to capitalism, providing not only an influx of capital but also disciplining hardship into workers (a form of "apprenticeship" to the capitalist industrial plant). The more "recent" argument of a "moral shift" (the basis of the previous lines of this article) is described by Hardt and Negri as an "ideological" apparatus in order to eliminate the sentiment of guilt in western society. Although moral arguments did play a secondary role, they usually had major resonance when used as a strategy to undercut competitors' profits. This argument holds that Eurocentric history has been blind to the most important element in this fight for emancipation, precisely, the constant revolt and the antagonism of slaves' revolts. The most important of those being the Haitian Revolution. The shock of this 1804 revolution introduced an essential political argument into the end of the slave trade as slaveholders in North America feared a similar situation could happen in the United States, where enslaved people in the Southern states might free themselves through an armed resistance movement and free all enslaved people. The success of enslaved and free blacks in Haiti in freeing themselves through revolt invoked fear among many whites in North America. St. George Tucker, a Virginian jurist, said this about the Haitian Revolution: "enough to make one shudder in fear of similar calamities in this country". Some white Americans and whites in the Caribbean suggested ending the slave trade and slavery to prevent an uprising like the one in Haiti. A Jamaican planter, Bryan Edwards, observed the Haitian revolution and argued that the enslaved people who revolted were newly imported slaves from Africa. Edwards and other planters believed the slave revolts in the Caribbean were instigated by these new slaves, and some abolitionists suggested ending the slave trade to prevent further slave insurrections. In Charleston, South Carolina, in 1822, Denmark Vesey and Gullah Jack planned a slave insurrection inspired by the Haitian Revolution.

The Haitian Revolution affected France's colonial economy. Saint Domingue (Haiti) was France's wealthiest colony and the world's top producer of sugar and coffee; it was also a global leader in cacao and indigo. Enslaved labor made Saint Domingue the wealthiest colony in the world and furnished two-thirds of France's overseas trade—because of Saint Domingue's wealth it was nicknamed "Pearl of the Antilles." After free and enslaved people gained their independence from France, France and French slaveholders wanted financial compensation from Haiti in the amount of 150 million francs to compensate for their lost wealth, calling it an "Independence Debt" because France had lost its wealthiest colony when Haiti gained independence. Haitians defeated the French, British, and Spanish during the revolution. Prior to the revolution, the United States was a major trade partner with Saint Domingue. After the revolution, the United States refused to recognize Haiti as an independent Black nation. Haiti was no longer the main exporter of sugar after the revolution, Cuba became the main supplier of sugar to foreign nations, and Louisiana became a center of sugar production in the United States. Slave revolts affected the economy of the slave trade as slaveholders lost property in enslaved people through death, running away, and a decrease in the production of cash crops resulting in a shift in trade to other nations.

However, both James Stephen and Henry Brougham, 1st Baron Brougham and Vaux, wrote that the slave trade could be abolished for the benefit of the British colonies, and the latter's pamphlet was often used in parliamentary debates in favour of abolition. William Pitt the Younger argued on the basis of these writings that the British colonies would be better off, in their economic position as well as in their security, if the trade was abolished. Consequently, according to historian Christer Petley, abolitionists argued, and even some absentee plantation owners accepted, that the trade could be abolished "without substantial damage to the plantation economy". William Grenville, 1st Baron Grenville argued that "the slave population of the colonies could be maintained without it". Petley points out that government took the decision to abolish the trade "with the express intention of improving, not destroying, the still-lucrative plantation economy of the British West Indies."

In 1787, the British helped 400 freed slaves, primarily African Americans freed during the American Revolutionary War who had been evacuated to London, to relocate to Sierra Leone. Most of the first group of settlers died due to disease and warfare with Indigenous peoples. About 64 survived to establish the second "Province of Freedom" following the failed first attempt at colonization between 1787 and 1789.

In 1792, 1200 Nova Scotian Settlers from Nova Scotia settled and established the Colony of Sierra Leone and the settlement of Freetown; these were newly freed African Americans and their descendants. Many of the adults had left Patriot owners and fought for the British in the Revolutionary War. The Crown had offered slaves freedom who left rebel masters, and thousands joined the British lines. More than 1,200 volunteered to settle and establish the new colony of Freetown, which was established by British abolitionists under the Sierra Leone Company.

In 1816, a group of wealthy European-Americans, some of whom were abolitionists and others who were racial segregationists, founded the American Colonization Society with the express desire of sending liberated African Americans to West Africa. In 1820, they sent their first ship to Liberia, and within a decade around two thousand African Americans had been settled there. Such resettlement continued throughout the 19th century, increasing following the deterioration of race relations in the Southern states of the US following Reconstruction in 1877.

The American Colonization Society's proposal to send African Americans to Liberia was not universally popular among African Americans, and the proposal was seen as a plot to weaken the influence of the abolitionist movement. The scheme was widely rejected by prominent African-American abolitionists such as James Forten and Frederick Douglass.

The Rastafari movement, which originated in Jamaica, where 92% of the population are descended from the Atlantic slave trade, has made efforts to publicise the slavery and to ensure it is not forgotten, especially through reggae music.

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In 1998, UNESCO designated 23 August as International Day for the Remembrance of the Slave Trade and its Abolition. Since then there have been a number of events recognizing the effects of slavery.

At the 2001 World Conference Against Racism in Durban, South Africa, African nations demanded a clear apology for slavery from the former slave-trading countries. Some nations were ready to express an apology, but the opposition, mainly from the United Kingdom, Portugal, Spain, the Netherlands, and the United States blocked attempts to do so. A fear of monetary compensation might have been one of the reasons for the opposition. As of 2009, efforts are underway to create a UN Slavery Memorial as a permanent remembrance of the victims of the Atlantic slave trade.

In 1999, President Mathieu Kerekou of Benin (formerly the Kingdom of Dahomey) issued a national apology for the role Africans played in the Atlantic slave trade. Luc Gnacadja, minister of environment and housing for Benin, later said: "The slave trade is a shame, and we do repent for it." Researchers estimate that 3 million slaves were exported out of the Slave Coast bordering the Bight of Benin.

Denmark had a foothold in Ghana for more than 200 years and trafficked as many as 4,000 enslaved Africans per year. Danish Foreign Minister, Uffe Ellemann-Jensen declared publicly in 1992: "I understand why the inhabitants in the West Indian Islands celebrate the day they became part of the U.S. But for Danish people and Denmark the day is a dark chapter. We exploited the slaves in the West Indian Islands during 250 years and made good money on them, but when we had to pay wages, we sold them instead, without even asking the inhabitants (...) That really wasn't a decent thing to do. We could at least have called a referendum, and asked people which nation they wanted to belong to. Instead we just let down the people."

On 30 January 2006, Jacques Chirac (the then French President) said that 10 May would henceforth be a national day of remembrance for the victims of slavery in France, marking the day in 2001 when France passed a law recognising slavery as a crime against humanity.

President Jerry Rawlings of Ghana apologized for his country's involvement in the slave trade.

At a UN conference on the Atlantic slave trade in 2001, the Dutch Minister for Urban Policy and Integration of Ethnic Minorities Roger van Boxtel said that the Netherlands "recognizes the grave injustices of the past." On 1 July 2013, at the 150th anniversary of the abolition of slavery in the Dutch West Indies, the Dutch government expressed "deep regret and remorse" for the involvement of the Netherlands in the Atlantic slave trade. The municipal government of Amsterdam, which co-owned the colony of Surinam, and De Nederlandsche Bank, which was involved in slavery between 1814 and 1863, apologized for their involvement on 1 July 2021 and 1 July 2022, respectively.

A formal apology on behalf of the Dutch government was issued by Prime Minister Mark Rutte in 2022 following a review by an advisory committee. Government ministers were sent to seven former colonies to reiterate the Dutch state's formal apology. Some activists continued to call for Willem-Alexander of the Netherlands to issue an apology.

In 2009, the Civil Rights Congress of Nigeria wrote an open letter to all African chieftains who participated in trade calling for an apology for their role in the Atlantic slave trade: "We cannot continue to blame the white men, as Africans, particularly the traditional rulers, are not blameless. In view of the fact that the Americans and Europe have accepted the cruelty of their roles and have forcefully apologized, it would be logical, reasonable and humbling if African traditional rulers ... [can] accept blame and formally apologize to the descendants of the victims of their collaborative and exploitative slave trade."

On 9 December 1999, Liverpool City Council passed a formal motion apologising for the city's part in the slave trade. It was unanimously agreed that Liverpool acknowledges its responsibility for its involvement in three centuries of the slave trade. The city council has made an unreserved apology for Liverpool's involvement and the continual effect of slavery on Liverpool's black communities.

On 27 November 2006, British Prime Minister Tony Blair made a partial apology for Britain's role in the African slavery trade. However African rights activists denounced it as "empty rhetoric" that failed to address the issue properly. They feel his apology stopped shy to prevent any legal retort. Blair again apologized on 14 March 2007.

On 24 August 2007, Ken Livingstone (Mayor of London) apologized publicly for London's role in the slave trade. "You can look across there to see the institutions that still have the benefit of the wealth they created from slavery," he said, pointing towards the financial district, before breaking down in tears. He said that London was still tainted by the horrors of slavery. Jesse Jackson praised Mayor Livingstone and added that reparations should be made.

In 2020, the Bank of England apologized for the role of directors in the Atlantic slave trade and pledged to remove pictures and statues of the 25 bank leaders who owned or traded in slavery.

On 24 February 2007, the Virginia General Assembly passed House Joint Resolution Number 728 acknowledging "with profound regret the involuntary servitude of Africans and the exploitation of Native Americans, and call for reconciliation among all Virginians". With the passing of that resolution, Virginia became the first of the 50 United States to acknowledge through the state's governing body their state's involvement in slavery. The passing of this resolution came on the heels of the 400th-anniversary celebration of the city of Jamestown, Virginia, which was the first permanent English colony to survive in what would become the United States. Jamestown is also recognized as one of the first slave ports of the American colonies. On 31 May 2007, the Governor of Alabama, Bob Riley, signed a resolution expressing "profound regret" for Alabama's role in slavery and apologizing for slavery's wrongs and lingering effects. Alabama is the fourth state to pass a slavery apology, following votes by the legislatures in Maryland, Virginia, and North Carolina.

On 30 July 2008, the United States House of Representatives passed a resolution apologizing for American slavery and subsequent discriminatory laws. The language included a reference to the "fundamental injustice, cruelty, brutality and inhumanity of slavery and Jim Crow" segregation. On 18 June 2009, the United States Senate issued an apologetic statement decrying the "fundamental injustice, cruelty, brutality, and inhumanity of slavery". The news was welcomed by President Barack Obama.

• Voyages: The Trans-Atlantic Slave Trade Database Archived 2019-07-05 at the Wayback Machine
• Quick guide: The slave trade – BBC News
• Slave Trade and Abolition of slavery – Teaching resources at Black History 4 Schools
• British documents on slave holding and the slave trade, 1788–1793