Seymour is a city in Jackson County, Indiana, United States. Its population was 21,569 at the 2020 census.

The city is noted for its location at the intersection of two major north–south and east–west railroads, which cross each other in the downtown area. The north–south line (the Jeffersonville, Madison and Indianapolis Railroad) was built in the 1840s and connected Indianapolis to the Ohio River at Jeffersonville. In 1852, Captain Meedy Shields persuaded a railroad into routing the east-west railroad (the Ohio and Mississippi Railroad) through his land. The first settlers arrived in the spring of 1853.

The companies Aisin USA and Rose Acre Farms are headquartered in Seymour, and Cummins operates a plant in the area. Walmart operates a large distribution center east of the city near the junction of I-65 and US-50. The city is also home to the 2nd largest high school gymnasium in the United States by seating capacity. The city is home to a historically significant former military airbase built during WWII that is now a civilian airport.

The land near Seymour was originally inhabited by the Cherokee Indians. The Treaty of Grouseland in 1805 opened the area to white settlers. Following the Pidgeon Roost Massacre in 1812, a local skirmish known as the Battle of Tipton's Island took place between settlers and a group of hostile Indian raiders. Between 1811 and 1815, Native Americans killed fifteen settlers. By 1816, only five families remained in the area. In 1817, the State of Indiana established a blockhouse to facilitate trade with the Lenape Indians until the natives ceded the area after the Treaty of St. Mary's. From 1822 to 1832, the county experienced significant depopulation.

Seymour was established and mapped out on April 27, 1852, by Meedy and Eliza Ewing Shields, near the 1809 Indian Treaty Corner and about two miles south of Rockford, Indiana. This location was the terminus of the north-south railroad at the Driftwood River before the purchase of 1828, and the construction of the rail bridge over the White River. In the late 1840s, a north-south railroad connecting the Ohio River at Jeffersonville with Indianapolis was built, crossing the Shields' farm. In 1852, an east-west railroad was being surveyed through Jackson County, and Meedy Shields convinced the Ohio and Mississippi Railroad to pass through his property. In return, he agreed to name the town after the railroad's civil engineer, Henry C. Seymour, although some sources mention J. Seymour, the surveyor. Contradicting this, another account states that in 1852, Captain Meedy Shields persuaded Hezekiah Cook Seymour to route the east-west Ohio and Mississippi Railroad through his land, naming the city in Seymour's honor.

The first settlers arrived in the spring of 1853. On June 29, 1854, the first train on the new Ohio and Mississippi Railroad stopped in Seymour and fired a celebratory cannon shot. Unfortunately, four men were killed in the resulting explosion from the poorly aimed fusillade.

Seymour was mockingly called a "mule crossing" due to its slow initial growth and the lack of interest from railroad companies. Significant development didn't occur until 1857, when the state legislature, influenced by local landowner and Indiana State Senator Meedy Shields, passed a law requiring all trains to stop at railroad intersections. This law, aimed at increasing safety before the widespread use of semaphores, boosted the value of land around these intersections and made them safer for warehousing.

Meedy Shields placed advertisements in the nearby Cincinnati and Louisville newspapers, offering a free lot and $100 to any congregation willing to establish a church in the city. Charles White of the Presbyterian Church was the first to respond in 1855. In 1858, Blish Mill became the town's first mill. By 1881, Seymour had three mills within its city limits. The large grain tower still stands near the railroad intersection in the center of town.

Seymour was once a stop on the Underground Railroad. On April 20, 1860, an Adams Express package shipped from Nashville, Tennessee, and addressed to "Hannah Johnson [care of] Levi Coffin" burst open at Seymour while en-route to Cincinnati. Levi Coffin was a leading Hoosier abolitionist and the unofficial leader of the Underground Railroad. The package contained a person fleeing slavery and seeking freedom in the North. A similar incident had occurred earlier in Kentucky. The true identity of "Hannah Johnson" remains a mystery. Although Indiana was a "free state", Article XIII of the state constitution of 1851 made it illegal for African Americans to settle in Indiana, and the Fugitive Slave Act permitted bounty hunters to capture and return people to slavery. The fugitive, later identified as Alexander McClure, was arrested and returned to Louisville and then to his owner in Nashville, Tennessee.

During the American Civil War, despite southern Indiana's strong Copperheads political sentiment, the city of Seymour and the surrounding area raised three separate infantry regiments for service in the Union Army. Volunteers from Seymour were organized at Camp Heffron in Seymour. The entirety of the 50th Indiana Infantry Regiment was commanded by former Indiana Secretary of State, Colonel Cyrus L. Dunham, as well as portions of the 10th Indiana Cavalry Regiment. Captain Fielder A Jones, who would end the war as a Brigadier General, led company H of the 6th Indiana Infantry Regiment.

By 1865, Fielder Jones of the 8th Indiana Cavalry was promoted to colonel, only a couple of months before being brevetted to Brigadier General. Early in the war, Jones had been "body shot" by a bushwhacker he later killed, W. A. Carter recalled decades later. "No Surrender" Jones survived his wound, then later raised another infantry unit of Jackson County men who elected him colonel. "When the company was organized, a group of Seymour women made a beautiful silk American flag and presented it to the Colonel. The presentation was made on the platform of what was then the O&M railroad station located in what [later became] the east warehouse of the Travis Carter Company at the corner of Fourth and Broadway. Mrs. George Williams, wife of one of Seymour's first jewelers, made the presentation speech. 'The enemy will never get this flag while I live,' the Colonel declared in accepting the flag and he kept his word." Carter said the flag came back with General Jones and his company, but other stories said Jones never returned to Seymour. After being mustered out, Jones headed to Missouri to practice law.

In 1863, Captain Meedy Shields trained local minutemen militia units in response to Morgan's Raid while several regiments of infantry were sent from the state capitol in Indianapolis.

Due to its strategic location along rail lines, and with the large cities of Indianapolis, Chicago, and Detroit to the north and St. Louis to the west, Seymour was an important waypoint for the movement of men and supplies to the front during the war. On January 20, 1864, during the transfer of Confederate prisoners of war, six officers escaped. One was later recaptured in town. The New York Times reports that on January 22, 1864, a "Soldier's riot" took place, wherein two soldiers were killed, and several others were injured.

The 50th Indiana Infantry Regiment lost 3 officers and 54 enlisted men killed and mortally wounded and 3 officers and 158 enlisted men by disease for a total of 218 casualties during the war. Colonel Dunham, a Democrat, was accused of harboring Confederate sympathies and mustered out of the regiment in 1863 under a cloud of suspicion. Lt. Colonel Heffron, who was poorly regarded by the men of the regiment, was also dismissed from the army and replaced by Major Samuel T Wells, a Vallonia, Indiana, native, Mexican-American war veteran, and former Jackson County Sheriff. Wells would go on to command the regiment after Durham's resignation until the 50th was dissolved and all men transferred to the 52nd Indiana Infantry Regiment which was also garrisoned in Mobile, Alabama, and remained there until the war's end.

During the Civil War, Seymour and Jackson County fielded a total of 2,571 volunteers for the Union cause.

After the war, local veterans organized the Ellsworth Post 20 of the G.A.R. At its zenith, the post included two hundred and twenty-two local citizens who had served the Union during the war as members. During its long existence, the organization included many prominent community members. The Ellsworth Post was active in local charities, organized burial services for local veterans, and conducted official observances on Decoration Day. The final member of the post, James H Boak, lived to be 98 years old. He died in 1942, closing one of the longest-running G.A.R. chapters in existence.

An infamous local murder occurred in January 1866, when a traveling merchant, Moore Woodmansee, 42, on his way to Cincinnati, disappeared while staying at the Rader House. The Rader House was operated by proprietor Captain George Rader, a purported Reno Associate, and was the center of gambling, theft, prostitution, and a string of mysterious disappearances. Months after he disappeared, the headless body of Woodmansee was found downriver in the East Fork of the White River; then known as the Driftwood River. Rader was implicated in the murder. Two local witnesses were murdered. Rader and his son-in-law were ultimately acquitted but forced to leave town.

A robbery of the Adams Express Car on the east-west Ohio and Mississippi line near Brownstown was reported in July 1866. That night, the perpetrators were chased by a local vigilance committee of 300 men that continued into the Rockford area. Three days later, the Reno brothers had been identified as the gang's leaders and newspapers were recounting the notorious deeds of the family. Later that year, Seymour was the site of the world's first successful peacetime train robbery, in which the train was moving. It was committed by the local Reno Gang, on October 6, 1866, just east of town, starting in the Adams Express Company car of the Ohio and Mississippi Railroad. Some members of the gang were later lynched at Hangman's Crossing outside town. The insolvent Ohio and Mississippi Railroad was reorganized in 1867 as the Ohio and Mississippi Railway.

About 1876, a general strike of approximately 500 railroad men occurred at Seymour and nearby North Vernon, Indiana, led by armed brakemen, engineers, and other railroad employees who had not been paid for two and a half months by the Ohio and Mississippi Railroad. A paper reported that the communities of Seymour and North Vernon were armed and in revolt. A contingent of US Marshals and detectives was sent from Cincinnati to end the strike. All passenger and cargo service through Seymour and North Vernon was suspended during the strike. The Ohio and Mississippi Railway was purchased in 1893 by B&O Southwestern Railroad.

The town's first high school was built in 1871 on the vacant lot of the disbanded civil war encampment. Frank B Shields, a Seymour native, former MIT professor, and inventor of Barbasol shaving cream, subsequently donated the adjacent land needed for the construction of the James Shields memorial gym.

In 1880, the Seymour Weekly Democrat noted that Seymour boasted a population of nearly 5,000, four schools including Shields High School, a Catholic School and two German schools with 700 students; four hotels including the newly built Hotel Jonas, the Faulconer, the City Hotel and the Mansion House.

During the years prior to the turn of the 20th century, Seymour saw a significant influx of Dutch and German migrants of the Lutheran faith. These migrants eventually established many successful local farms and businesses. These pioneers' influence continues today and can be seen in the city's annual Oktoberfest celebration.

Seymour fielded its own minor league team, the Seymour Reds, beginning in 1900. Pee Wee Reese once played with the Seymour Reds before being called up to the majors. The team had its own field, Redlands Park, north of Shields City Park.

The Ahlbrand Carriage Company, a builder of buggies and custom coaches was incorporated in Seymour by Ephriam, Albert, and Walter Ahlbrand of Seymour.

The Seymour Public Library opened to the public in January 1905, following a grant of $10,000 from the Carnegie Foundation in 1903 led by the Public-School Superintendent and President of the Seymour Public Library Board, Professor H.C. Montgomery. Efforts to bring a library to Seymour began twenty years early in 1881. Early library collections were housed in a local bookshop and then at Shields High School until the new Carnegie Library opened. The public library was part of more than $2.6 million in grants issued in the state of Indiana for more than 160 libraries: more than any other state.

In 1913, the Great Flood hit Seymour causing widespread death and destruction. It was the deadliest natural disaster to ever hit the area. The East Fork of the White River reached 27.50 feet (8.38 m) above the level recorded in the flood of 1884.

In 1914, H. Vance Swope, a landscape artist who spent his youth in Seymour, donated many of his own works and paintings he acquired during his career to Seymour's Art League. Eventually, those works became part of the H. Vance Swope Gallery in the new Public Library. This collection contains important works by Charlotte B. Coman and other favorites from Swope.

On May 7, 1915, leading city-industrialist and scion of the Thompson family, Eldridge Blish Thompson died during the sinking of the ocean liner RMS Lusitania. A memorial scholarship was funded in his name by his family at Seymour's Shields High School for any student accepted to Yale University. The sinking of the ocean liner was an important factor in President Woodrow Wilson's decision to ask Congress for a declaration of war in April 1917.

During World War I, nine Seymour natives died in combat. Seymour's first municipal airport, the White River Valley Flying Field, was located on the Henry Ahlert farm (once owned by the Renos) near the White River north of the city.

In 1934, Seymour police officer John Pfaffenberger was shot and killed by three assailants after he attempted to stop their car after they stole a few dollars' worth of fuel from a gas station east of town. One defendant, Nashville, Indiana, native Edward Coffin, was subsequently sentenced to death and sent to Indiana's electric chair for the murder of Officer Pfaffenberger. His co-defendants were sentenced to lengthy prison terms.

Kenneth Earl Cockrum, serving on the U.S.S. Arizona became the first casualty of the war from Seymour. During World War II, the US government purchased 2,500 acres (1,000 ha) of land southwest of town for use as an airfield. Local veterans initially proposed to name the field after US Navy Seaman Cockrum who died at Pearl Harbor. Freeman Army Airfield operated from 1942 to 1946. The base was first used for twin-engine training. The first class graduated on April 29 and went on to fly multi-engine aircraft such as the B-24 Liberator, B-17 Flying Fortress, B-29 Superfortress, and various other medium bombers and transport aircraft. Twin-engine training continued with a total of 19 classes of students graduating from Freeman Field using a total of 250 Beechcraft AT-10 Wichita trainers. The last graduates were in May 1944; 4,245 total cadets.

Freeman Army Airfield was the first helicopter base in the US. The first instructor pilots arrived on June 30 and preparations for the helicopter training were made in great secrecy, as in 1944 very few people had seen one and the technology was new and revolutionary. The group assigned to coordinate their arrival was known as "Section B-O". A total of six Sikorsky R-4 helicopters were assigned for training, flown directly to Freeman from the Sikorsky plant at Bridgeport, Connecticut. This was the longest-distance flight of any formation of helicopters at the time.

The Freeman Field Mutiny occurred in 1945, in which African American members of the 477th Bombardment Group attempted to integrate an all-white officers' club at Freeman Army Air Corps Base. The mutiny is generally regarded by historians of the Civil Rights Movement as an important step toward full integration of the armed forces and as a model for later efforts to integrate public facilities through civil disobedience.

Nearing the end of WWII, Freeman Field was designated the Foreign Aircraft Evaluation Center for US Army Air Technical Intelligence. After the end of the war in Europe, captured German and Italian aircraft were collected by "Operation Lusty". Freeman Field was also charged with the mission to receive and catalog United States equipment for display at the present and for the future AAF museum. However, these operations, including the helicopter training missions were moved to other locations, and Freeman Field was deactivated and deeded to the city of Seymour in 1946. Future astronaut Gus Grissom enlisted as an aviation training cadet at Freeman Field in 1944.

During the last week of June 1952, the city of Seymour held a week-long centennial celebration that included concerts, parades, a re-enactment of the Reno Brothers train robbery, contests, and a play entitled "The Seymour Story". The B&O Railroad loaned Engine #25 and several cars from their Baltimore Museum for use in the Reno reenactment scenes, and the event was featured in B & O Magazine. During the event, local industries paid their employers in silver dollars to commemorate the event.

Beginning in 1959, the city's former high school, Shields High School, was closed and all students transferred to the new Seymour High School west of town. By 1970, the school corporation completed the construction of the second-largest school gymnasium in the United States. In 1981, the gym was renamed the "Lloyd E Scott" gymnasium in honor of the Indiana Hall of Fame basketball coach.

Police Officer Donald M Winn was killed in the line of duty on November 7th, 1961, during a botched robbery. His murderer was convicted and sentenced to life in prison. Officer Winn's widow received the National Police Officer Association's Medal of Merit for Valor, the organization highest award, on his behalf during ceremonies later that year.

Shortly after opening a local franchise in the area, on October 20, 1965, during a ceremony in Seymour, Colonel Harland Sanders, owner and originator of Kentucky Fried Chicken was initialed as a member alongside thirteen local residents into the local Elks Lodge, #462. Sanders had a long association with Seymour through cousins and a nephew living in town.

Seven Seymour servicemen were killed in action during the Vietnam War. The highest-ranking soldier killed in action from Seymour was Command Sergeant Major William Henry Clevenger, United States Army who enlisted in the United States Army during World War II. He was awarded the Silver Star and the Distinguished Flying Cross.

In 1970, future Rock and Roll Hall of Famer John Mellencamp graduated from Seymour High School and briefly attended nearby Vincennes University before returning to Seymour and working for the local telephone company while pursuing a music career. Led by Mellencamp's new management and record label, the city of Seymour dedicated its Oktoberfest parade to young Mellencamp on October 2, 1976. On that day, the mayor declared it "Johnny Cougar Day," and the city celebrated by parading "Johnny Cougar" through downtown to help promote his debut album, the Chestnut Street Incident.

Various murders occurred in the Seymour area that were linked to Rose Acre Farms in the 1970s. Employees Theresa Osborne, Mike Reece, and Carrie Croucher all from Rose Acre with ties to founder David Rust died under mysterious circumstances. Mysteriously, Theresa Osborne's body was found in the trunk of her burnt and abandoned vehicle weeks after her disappearance. Even years later, the deaths remained under investigation. Louisville Courier Journal reporters published a series of articles. Investigations by local authorities into the deaths did not result in any charges against David Rust, who died in 2004.

Seymour police officer Jack Osborne died after being hit by a motorist at the scene of a traffic accident on Interstate 65 on August 15, 1981. Sadly, he was the third Seymour police officer to die in the line of duty.

After being found guilty of four counts of accepting bribes while in office, Christopher Moritz resigned as mayor on March 29, 1983. Because he was sentenced to five years in prison and barred from holding public office for ten years until William Bailey assumed office. Donald Scott served the remaining balance of Moritz's term as Mayor. Moritz began serving his sentence on December 8, 1984.

On March 29, 1983, Christopher Moritz resigned as mayor after a judge found him guilty of four counts of accepting bribes while in office. He was sentenced to five years in prison and barred from holding public office for ten years. Moritz began serving his sentence on December 8, 1984. Donald Scott served the remaining balance of Moritz's term until William Bailey assumed office.

In 1985, Mellencamp released "Small Town" a song written about his hometown. It reached #6 on the U.S. Billboard Hot 100 chart. MTV included the associated music video in frequent rotation. This video, and approximately five others, were filmed in around the Seymour area during this time. The videos included shots of Riverview Cemetery, Rockford, the Rok-Sey Arena, downtown Seymour, and cameos of many locals. This, with the release of his "Rain on the Scarecrow" single and music video, increased awareness of the plight of rural American farmers in general and life in Seymour specifically. Many regional and national media outlets produced segments about Seymour during this timeframe.

Future Indiana University basketball coach Teri Moren graduated from Seymour High School in 1987 and was named an Indiana All-Star that year. She led the Seymour Owls to four sectional titles, two regional championships, a semi-state win, and a 1987 state finals appearance.

Seymour's east-west railroad, controlled by the Baltimore and Ohio Railroad since the previous century merged in 1987 into CSX Transportation, creating one of the largest Class I railroads in North America.

In 1989, the Stardust Theater, a local landmark for fifty years, shuttered its gates for the last time. The 550-spot drive-in first opened on May 19, 1949, and aired its last feature films "Ghostbusters II" and "Karate Kid III" on September 30. The theater was popular for showing movies, cartoons, and dusk-to-dawn movie marathons. The operator of the theater said the decision to close the theater was purely economic, the land the theater sat on was just too valuable. The owner, Florence Carter sold the property to developers who turned the entire site into an outlet mall.

On July 8, 1991, the former Lynn Hotel, a local landmark first opened on July 1, 1883, collapsed due to disrepair and neglect. The city previously purchased the property for $35,000 with an eye on redeveloping the building into city offices. Other groups had offered to purchase and save the property before it was leveled including John Mellencamp, an investment group from California, and local community activists.

Despite efforts from local community leaders, the city of Seymour and then-mayor John Burkhart ordered the leveling of the historic Vondee Theater on September 24, 1993. Marina Gill, President of the Historic Preservation Foundation said, "This is just negligence" when asked about the decision to level the structure.

On May 29, 1997, the former Shields High School, first constructed in 1910, was raised during a botched demolishment of a smaller portion of the building, the girls' gym. The structure was privately owned after the construction of Seymour Middle School, and once housed a private bible college. Building inspectors determined that was too much damage and the structure was unsafe.

On Christmas Day 1998, the historic Walton Hotel, first known at the Rader House, and then the Faulkner House, the Jonas Hotel, and the Centennial Hotel, burned to the ground in an accidental fire that killed one person. The property was first built in 1854, was one of the oldest structures in Seymour, was in the process of being restored, and was being used as low-income housing at the time of the fire. The structure was the third important historic downtown building to fall during the nineties.

Thanks to the efforts of then Lt. Governor John Mutz and community leaders at the Jackson County Industrial Development Corporation, Aisin constructed a factory in Seymour in 1986, with production beginning in 1989 with wide public support. Initial estimates suggested 200 new employees, but by 2020, Aisin employed more than 2,000 local residents. This factory has since been expanded and supplies components for Honda, General Motors, Mitsubishi, Nissan and Toyota.

The 106 mi (171 km) north-south railroad line that serves Seymour was purchased by the Louisville and Indiana Railroad from Conrail in March 1994. The Seymour Diamond Crossing is a good place to also watch the east-west railroad line, which CSX upgraded in 2016 for reliable higher speed operation. The Louisville and Indiana Railroad served as a short-line railroad to provide switching services for access to the CSX mainline.

Immigration from San Sebastián Coatán, Guatemala, began about 1989 as indigenous Chuj people found the American Dream in the United States. As word spread to their families and friends in their hometown about the quality of life in Seymour, more families journeyed from their poverty-stricken part of Guatemala to a newer, more fruitful life in the U.S. Immigrants from Guatemala as of 2020 make up more than 10% of the local population.

In November 2019, the city unveiled a large mural of John Mellencamp, painted on the side of a local guitar store. The store's owner, Larry McDonald, is a longtime friend and former bandmate of Mellencamp. The Mellencamp family donated $50,000 to help turn the former parking lot into a green space so more people could enjoy the mural painted by artist Sue Bliss.

In October 2024, Indiana Attorney General Todd Rokita issued a civil investigative demand to ensure the city complies with state immigration policies. Specifically, the AG requested records to determine if the city is acting as a De Facto sanctuary city and to produce data on individuals who may have committed the specific crime of driving without a license, as well as all misdemeanor violations except for driving without a license. On the same day, Seymour Mayor Matt Nicholson canceled a regularly scheduled city council meeting. In response, Seymour Common Council member Drew Storey held an impromptu community meeting to address concerns about the city's rapidly growing population. Census data shows that over the past 20 years, Seymour's Hispanic population increased from 4.8% to approximately 13%, and the overall population grew by about 3,000 people. "The growth that we've seen and experienced in just the past few years is exceeding our ability to deal with it, as we're seeing through other communities throughout the state," said State Representative and Seymour resident Jim Lucas. During the same twenty-year period, Seymour has seen an increase in crimes stemming from immigration; including the 2024 arrests of one undocumented immigrant for performing dentistry without a license, and a second for selling prescription medicine.

Hangman's Crossing, just west of Seymour near a property once owned by a farmer named 'H. Borchherding', a Beech tree once stood. This tree witnessed the final demise of the Reno Gang at the hands of a group of vigilantes allegedly led by town elder Travis Carter. The exact location of the tree is lost to time, but the Indiana Folklore Reader tells us it was near the Borcherding farm, across the road which crossed a tiny stream on 'the old Brownstown Road'. Legend has it that the hanging tree never bore leaves again and some say that Laura Reno had the tree burnt to the ground as nothing remains.

Local folklore tells us that somewhere near Seymour, the Reno Gang buried $96,000 from their last train robbery. Before it was torn down, the original Reno home near the Riverview Cemetery was an object of curiosity among fortune hunters who would sometimes find small silver coins where the house once stood.

After they were hanged, legend has it the Reno Brothers were allegedly buried together under a single stone alone atop a hill in the old city cemetery. Outraged, local citizens refused to bury their relatives with the Renos. The Riverview Cemetery was eventually built and many famous former occupants of the city cemetery, like town founder Meedy Shields and his wife Eliza, were laid to rest in Riverview. Later, a Reno plot with headstones for each of the brothers was constructed in the old cemetery close to the road to appease the tourists and the curious.

Another legend tells us of the demise of a train, its crew, and a passenger car that disappeared into the Blue Hole Quarry in 1913. The train met its fate during a rainstorm and flood that washed away the train trestle and everything on it. Despite the efforts of local authorities, the remains of the train or the crew have never been found.

In the March 31, 2001, copy of the Seymour Tribune, readers share their stories of "Martha's Grave", the burial site of an alleged witch, and one "can see her face in the moss on the north side of the tombstone".

Finally, Freeman field was home to captured Nazi aircraft after World War Two, including captured jet aircraft, and V-1 and V-2 rockets. However, the base was closed shortly thereafter, and the base commander ordered many aircraft to be buried at the site.

Seymour is located at 38°57′26″N 85°53′20″W / 38.95722°N 85.88889°W / 38.95722; -85.88889 (38.956350, -85.890068).

According to the 2010 census, Seymour has a total area of 11.425 square miles (29.59 km), of which 11.42 square miles (29.58 km) (or 99.96%) is land and 0.005 square miles (0.01 km) (or 0.04%) is water.

The soil is sandy but generally productive for agriculture and livestock. The local topology is dominated by the East Fork of the White River, a slow-moving, heavily silted, and meandering floodplain. Because of the surrounding low-lying swamplands and agricultural activity, the river is prone to frequent flooding averaging 19 days above flood stage per year; with at least three major floods recorded since 1900.

Seymour experiences a humid subtropical climate (Köppen classification "Cfa") characterized by high temperatures and evenly distributed precipitation throughout the year. Summers are influenced by moist maritime airflow, leading to warm, oppressive nights and convectional thunderstorms, with tropical cyclones enhancing rainfall in some regions. Winters are mild, with frosts not uncommon and precipitation primarily from frontal cyclones. The average annual temperature is 55.0°F (12.8°C), with July being the warmest month at 77.0°F (25°C) and January the coolest at 32.0°F (0°C). The highest recorded temperature is 113.0°F (45°C) in July, and the lowest is -22.0°F (-30°C) in January. Seymour receives an average annual precipitation of 41.9 inches (1064.3 mm), with March being the wettest month and October the driest. The area also averages 16.9 inches of snow annually, with January having the most snowfall.

Historical population

Census	Pop.	Note	%±
1860	966		—
1870	2,372		145.5%
1880	4,250		79.2%
1890	5,337		25.6%
1900	6,445		20.8%
1910	6,305		−2.2%
1920	7,348		16.5%
1930	7,508		2.2%
1940	8,620		14.8%
1950	9,629		11.7%
1960	11,629		20.8%
1970	13,352		14.8%
1980	15,050		12.7%
1990	15,576		3.5%
2000	18,101		16.2%
2010	17,503		−3.3%
2020	21,569		23.2%
Source: US Census Bureau

As of the census of 2020, there were 21,569 people and 7,866 households in the city. The population density was 1,532.7 inhabitants per square mile (591.8/km). The racial makeup of the city was 82.2% White, 2.0% African American, 0.2% Native American, 4.3% Asian, 0.1% Pacific Islander, and 2.3% from two or more races. Hispanic or Latino of any race were 13.0% of the population.

The median household income in the city was $47,949 compared to the median household income of $62,743 in the State of Indiana. 39% of the population was employed in manufacturing or production and 17.4% of the population was involved in the education or healthcare industry.

The median age in the city was 34.4 years. 28.4% of residents were under the age of 18; 6.3% were between the ages of 18 and 24; 69.1% were aged 21 and over.

The 2020 Census estimates that 7% of the population were veterans.

As of the census of 2010, there were 17,503 people, 6,907 households, and 4,514 families living in the city. The population density was 1,532.7 inhabitants per square mile (591.8/km). There were 7,719 housing units at an average density of 675.9 per square mile (261.0/km). The racial makeup of the city was 90.3% White, 1.3% African American, 0.2% Native American, 1.2% Asian, 0.1% Pacific Islander, 5.1% from other races, and 1.8% from two or more races. Hispanic or Latino of any race were 11.5% of the population.

There were 6,907 households, of which 34.4% had children under the age of 18 living with them, 45.3% were married couples living together, 13.5% had a female householder with no husband present, 6.5% had a male householder with no wife present, and 34.6% were non-families. 28.1% of all households were made up of individuals, and 9.8% had someone living alone who was 65 years of age or older. The average household size was 2.49 and the average family size was 3.01.

The median age in the city was 35.5 years. 25.3% of residents were under the age of 18; 8.7% were between the ages of 18 and 24; 28.6% were from 25 to 44; 24% were from 45 to 64; and 13.4% were 65 years of age or older. The gender makeup of the city was 48.7% male and 51.3% female.

As of the census of 2000, there were 18,101 people, 7,231 households, and 4,743 families living in the city. The population density was 1,670.3 inhabitants per square mile (644.9/km). There were 7,709 housing units at an average density of 711.4 per square mile (274.7/km). The racial makeup of the city was 93.4% White, 1.0% African American, 0.3% Native American, 1.4% Asian, 0.1% Pacific Islander, 2.9% from other races, and 0.9% from two or more races. Hispanic or Latino of any race were 4.9% of the population.

There were 7,231 households, out of which 32.6% had children under the age of 18 living with them, 49.4% were married couples living together, 11.5% had a female householder with no husband present, and 34.4% were non-families. 28.5% of all households were made up of individuals, and 11.6% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 2.99.

In the city, the population was spread out, with 25.5% under the age of 18, 10.2% from 18 to 24, 31.4% from 25 to 44, 19.4% from 45 to 64, and 13.5% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 95.7 males. For every 100 females aged 18 and over, there were 93.0 males.

The median income for a household in the city was $36,883, and the median income for a family was $43,357. Males had a median income of $30,638 versus $22,265 for females. The per capita income for the city was $18,222. About 8.0% of families and 10.0% of the population were below the poverty line, including 9.7% of those under age 18 and 11.6% of those age 65 or over.

The economy of Seymour is based primarily on manufacturing and distribution, healthcare, and education. Major manufacturers include Aisin USA, a leader in the field of automotive component manufacturing, Cummins, Valeo North America, the Lannett Company, and Silgas Plastics. Home Products Incorporated recently acquired the former Lear Siglar facility that sits atop the defunct Milwaukee Rail yard. Nippon Steel Pipe America, an automotive parts supplier, employs over 400 associates at its plant in Seymour.

Owing to the city's convenient access to I-65 and US-50, Walmart Transportation and Pet Supplies Plus have significant operations based in Seymour. Walmart Distribution is the primary provider of merchandise for all Wal-Mart retail units. The Walmart Distribution Center is fully mechanized and multi-shift operated with receiving, order filling, and shipping departments.

Schneck Medical Center employs more than 1,100, including 200 physicians and 400 volunteers, and has operated for over 100 years. The Seymour Community Schools and Rose Acre Farms round out the list of major employers.

Other employers include retail and service industry providers including franchise and locally owned restaurants that line US-50 headed east out of the city.

Mayors are elected by city-wide election every four years from qualified candidates who are residents of the city. The first mayor of the city was Captain George Greene, a native of Kentucky, a veteran of the Mexican-American War, and a close ally of Meedy Shields. The City Hall has operated out of the former Southern Indiana Telephone and Telegraph Company since 1985.

In 2019, a local businessman, former city councilman, 1996 graduate of Seymour High School, and 1998 graduate of Ivy Tech, Matthew Nicholson was elected to his first term as mayor. He carried the election with 1,963 (59.3%) votes versus challenger Rexanne Ude who received 1,350 (40%) votes. Since his election, in addition to his official duties, Nicholson has joined the board of directors for Main Street Seymour, Indiana and regularly contributes to the local newspaper.

The seven-member city council is the legislative body for the city and has the exclusive responsibility of passing or changing local laws, resolutions, orders, and motions for the city's government. As the fiscal body, the Council has the authority to levy certain taxes and it has the sole responsibility of adopting a city budget each year. The Council also appoints members to certain boards and commissions that serve the community in various areas.

A chronological list of mayors of the city of Seymour includes;

Over the past two decades, Jackson County, Indiana, has consistently shown strong support for Republican candidates in presidential elections. The county has maintained a clear preference for the GOP. Notable Democratic contenders, including Barack Obama and Hillary Clinton, have garnered significant but lesser support. Libertarian candidates have also made their presence felt, though with smaller percentages. This trend underscores the county's political leanings and voting patterns over the years.

In Jackson County, Indiana, the election results for the 2024 Presidential Election, Republican Donald J. Trump secured a commanding victory with 14,430 votes (76.69%), followed by Kamala D. Harris with 4,035 votes (21.44%). Independant candidate Chase Oliver received 109 votes (0.58%), while Robert F. Kennedy Jr. garnered 209 votes (1.11%). There were also 34 write-in votes (0.18%).

In the 2020 election, Jackson County, Indiana, saw a decisive victory for President Donald Trump, who received 14,555 votes, accounting for 75% of the total votes. In contrast, Vice President Joe Biden garnered 4,302 votes, which represented 23% of the total votes.

In the 2016 election for Jackson County, Indiana, Donald Trump secured a commanding victory with 12,857 votes, accounting for 73.3% of the total votes. Hillary Clinton received 3,843 votes, which represented 21.9% of the total. Libertarian candidate Gary Johnson garnered 832 votes, making up 4.7% of the total votes.

In the 2012 election for Jackson County, Indiana, Republican candidate Mitt Romney secured a strong victory with 10,419 votes, accounting for 62.4% of the total votes. Incumbent President Barack Obama received 5,838 votes, which represented 34.9% of the total. Libertarian candidate Gary Johnson garnered 447 votes, making up 2.7% of the total votes.

In the 2008 election for Jackson County, Indiana, Republican John McCain won with 9,726 votes, accounting for 55.77% of the total votes. Democratic challenger Barack Obama received 7,354 votes, which represented 42.17% of the total. Libertarian candidates Bob Barr garnered 289 votes, making up 1.66% of the total votes. There were also 66 write-in votes (0.38%) and 5 votes for other candidates (0.03%).

In the 2004 election for Jackson County, Indiana, Republican George W. Bush won with 11,083 votes, accounting for 67.96% of the total votes. While Democrat John Kerry received 5,092 votes, which represented 31.22% of the total. Libertarian candidates Michael Badnarik and garnered 112 votes, making up 0.69% of the total votes. There were also 22 write-in votes (0.13%).

Seymour Community Schools operates Seymour High School and eight other elementary and secondary schools in the city. The current system-wide school enrollment exceed 5,000 students. The local schools employ 650 people and are managed by a public board consisting of seven members of the community. The current board President is Art Juergens, a retired social studies teacher and coach. Three hundred forty-two students graduated in the class of 2023.

Trinity Lutheran High School, a private educational institution for grades 9–12 that first opened in 2000 on a newly donated 41-acre campus. The school is owned and operated by the South Central Lutheran Association for Secondary Education, Inc., an association of 14 Lutheran congregations in Scott, Jennings, Bartholomew, and Jackson Counties. The school is accredited and in good standing by the National Lutheran School Accreditation (NLSA) organization of the Lutheran Church-Missouri Synod, Cognia, and also recognized as an accredited school by the Indiana Department of Education. Twenty-seven seniors graduated from TLHS's 19th class in May 2023.

The Immanuel Lutheran School provides private K-8 and is full accreditation through the State of Indiana and the Lutheran Church Missouri-Synod.  In addition to the core curriculum, Immanuel's comprehensive education offers a full fine arts program including music, band, art, and physical education. Students attending ILS have the option of enrolling in either Trinity Lutheran High School to finish their secondary education or enrolling at Seymour High School.

The St. Ambrose Catholic School is a private school associated with St. Ambrose Church of Seymour Indiana. The school is a member of the Archdiocese of Indianapolis. The current facility opened in 1958 but the Archdiocese has offered private Catholic educational services to the community since 1858. Enrollment is open for students K-8. The school is overseen by St. Ambrose School Commission is an advisory committee that works with the school principal and pastor on the advancement of the school.  The commission has nine members and meets six times per year. The school provides services in both English and Spanish. The school is fully accredited by the State of Indiana and nationally through Cognia.

Seymour Public Library, a branch of the Jackson County Public Library.

The recreation department of the city of Seymour operates five parks, including the 12-acre Shields Park that is home to a skate park and a public pool.

Shields Park is the oldest public park in the city and was formally known as City Park. It is located on North Park Street. In 1924, Anna M. Gaiser donated the site of her father's plant nursery to be Gaiser Park.

Kessler Park was donated by the Kessler family in 1978.

Additionally, the recreation department operates 3 plazas, one recreation field located near Freeman Field and Mellencamp Plaza below the large mural of John Mellencamp in the downtown area that was completed in 2019. The department also provides a memorial tree and bench program to honor deceased residents. In addition to the numerous parks, plazas, and recreational facilities, the recreation department also provides 14 miles of bike and walking trails around the city.

The Actors Community Theatre of Seymour (ACTS) is a non-profit organization founded in 2013. Its first production was in March 2014. ACTS is dedicated to the propagation and preservation of the theatrical arts in the area and has an ongoing schedule of theatrical performances.

The Southern Indiana Center for the Arts (SICA) is a not-for-profit organization operated by a volunteer board of directors and an executive director owned by the Mellencamp family since 1991 that provides art education and helps draw attention to the area of Jackson County as an art-conscious region.

The Oktoberfest celebrates the city's German heritage and has been held annually since 1973. The first Oktoberfest was organized by the Seymour Chamber of Commerce and featured Bavarian music, carnival rides, food and exhibit booths, parades, a hot air balloon race, baby contest and a Biergarten.

Scoop the Loop is a local weekend car show that started in 2011 but can trace its origins back to the years following WWII. In Seymour, like many small towns in America, with the rise of car culture, rock and roll, and teenagers with free time, cruising downtown to meet and make new friends and show off cars became a way of life in Seymour. Seymour used to be so popular for cruising that teens would come from eleven surrounding counties. But, starting in the 80s, some local merchants complained and alleged illegal activities were occurring. In the 90s, without any city ordinance to prohibit the activity, the local government would block many of the roads downtown and popular parking lots. This effectively killed the practice in Seymour as happened in nearby Columbus, North Vernon, and Seymour. But, cruising was reborn in 2011 by local cruising enthusiasts two started a yearly event held on one Saturday each August. Ironically, local merchants and restaurants support the event as a way to draw customers back to the downtown area.

The H. Vance Swope Memorial Art Gallery was created at the bequest of the artist, who spent his youth in Seymour and whose father was once the postmaster, and relative of then-mayor Allen Swope and contains works by regional artists as well as an extensive collection of landscapes by Swope.

Local comfort food is a deep part of Seymour's culture. This includes local hotspots like The Townhouse Cafe, which first opened in 1962. They have been serving locals their favorites for breakfast since then. In 2023, it was voted best home cooking, best breakfast, and best catering, and won honors for its tenderloins, burgers, and atmosphere. The Fish Stand, first opened its doors in 1962. Locals have been coming to the small unassuming local landmark restaurant on Ewing Street since then for fried fish and comfort food. The stand resides in a building first constructed in 1878 and needed major repairs when the current owners bought the property in 2013 that included new flooring, a new kitchen, and a new roof. Larrison's Diner, a local institution, has been serving local teenagers and adults-alike a steady diet of comfort food like burgers, fries, tenderloin sandwiches, and Big Red soda for more than fifty years. The diner was used as a filming location for Falling from Grace, starring John Mellencamp. The diner is also popular among his fans who might catch a glimpse of him at his favorite booth from time to time.

Until 2019, Seymour was the last town in the United States to celebrate Victory over Japan Day with a local parade. Beginning in 1946, the parade was held annually for 73 years until the local VFW voted to discontinue the tradition.

Seymour is home to many vibrant social, service and philanthropic organizations such as the Elks Lodge, the Jackson County Masonic Lodge, the Order of the Eastern Star, the Seymour Lions, the Rotary Society, the Moose Lodge, the Rotary Society, the Phi Beta Psi, Knights of Columbus, and the Jackson County Sertoma Club.

The city is home to six structures listed on the National Register of Historic Places. The Farmers Club was built by the Blish family and donated to the city as a memorial to city founder Meedy Shields and was included in the National Register in 1983. The building was constructed from Bedford limestone, brick, and steel and at the time of its construction it was the only building of its kind in the midwest. Meedy Shields Blish (1855–1922) was inspired to provide a local place of comfort and relaxation to area farmers while they were bringing produce and grain to market in the city. The building formally open on October 8, 1914. Since then it has been used as the club, the building also housed the Seymour Red Cross, the city of Seymour, the Seymour Police Department, and the Seymour Chamber of Commerce.

The First Presbyterian Church of Seymour was constructed in 1884 and is of Late Gothic Style architecture and includes stained glass by the Jacoby Art Glass Company. At the time of its construction, it was the tallest spire in the city. It was listed on the National Register of Historic Places in 1991.

The T. Harlan and Helen Montgomery House is a grade five historic building of Dutch Colonial Revival design located at 628 North Poplar Street has 5 bedrooms and 2 and a half baths. It last sold in 1979 for $49,000 and was placed on the registry in 2010.

The Seymour Commercial Historic District consists of 79 contributing buildings and 4 contributing structures in the central business district of Seymour. The district developed between about 1876 and 1945 and includes notable examples of Italianate, Romanesque Revival, and Classical Revival style architecture. The entire district was placed on the register in 1995 although the Jonas Hotel later burnt to the ground and no longer exists.

The Southern Indiana Railroad Freighthouse, has since January 2008 served as the Jackson County Visitor Center, for Jackson County, Indiana. The freight house was placed on the National Register of Historic Places on June 22, 2003.

George H. Vehslage House is a historic home located at 515 N. Chestnut Street. It was built in 1894 and is a 2-and-one-half-story, Queen Anne style brick dwelling with a limestone foundation. It was placed on the registry in 2010.

714 W Fifth Street is the boyhood home of John Mellencamp. The 2-bedroom, 1 bath, 1019 square foot ranch style house was built in 1949. It has been privately owned since 1979. The owner has plans to remodel the property and rent it on AirBnB.

The Travis Carter house at 410 Indianapolis Avenue is the oldest building (1852) still standing in Seymour. Today, it is privately owned, but it once housed the offices of the local Red Cross.

The Blish Mill grain towers are the tallest structures in town, they operated from 1858 to 1976.

The Federal Building was built in 1915, served for many years as the post office, and then as offices for the Seymour Police Department. Today, it is being restored as the Seymour Museum Center.

At the corner of N. Poplar and Sixth Street the former James Shields Memorial Gym is one of Indiana's ten most endangered landmarks. One of Indiana's largest high school gymnasiums when it was built by Works Progress Administration workers in 1941, the James M. Shields Memorial Gymnasium provided the backdrop for decades of local basketball memories, hosting 21 sectional titles from 1942 to 1970. A local family purchased the long-vacant property in 1996, and later had to demolish the high school nearby. As of 2023, the gym remains empty. Vandals continue to break windows and cover walls with graffiti, despite the current owner's attempts to secure the property. Though roof leaks have allowed water to infiltrate the building, an architectural assessment showed the steel and concrete gym to be structurally sound.

The Pennsylvania Railroad succeeded the Jeffersonville Railroad (built northward). A Chessie System caboose sits in front of the Blish Mill grain tower.

The Ohio and Mississippi Railway, built westward, was acquired by the Baltimore & Ohio Railroad in 1893. It has been operated by CSX since 1986.

The Evansville & Richmond Railroad (after 1910 the Chicago, Terre Haute & Southeastern Railroad (CTH&SE), or "the Milwaukee") was built eastward toward Richmond, reached Seymour in 1890, and connected with New York Central in Westport. Trackage east of Seymour was "cut off" in 1961, and operations to Bedford closed in 1978.

The Interstate Public Service interurban lines reached Seymour from Columbus in October 1907. Interstate merged into Midland United Company, leased to Indiana Railway, and all trains south of Seymour stopped running to Louisville in September 1939. Operations continued north of Seymour to Indianapolis until a collision on September 8, 1941, that wrecked "the majority of the line's rolling stock".

• Interstate 65