According to the U.S. Census Bureau, the county has a total area of 937.05 square miles (2,426.9 km), of which 934.17 square miles (2,419.5 km) is land and 2.88 square miles (7.5 km) (0.31%) is water.

State and local protected areas

• Moore Farms Botanical Garden (part)
• Wee Tee State Forest (part)
• Wee Tee Wildlife Management Area

Major water bodies

• Black Mingo Swamp
• Black River
• Great Pee Dee River
• Lake Swamp
• Muddy Creek
• Santee River
• Singleton Swamp

Adjacent counties

• Florence County – north
• Marion County – northeast
• Georgetown County – east
• Berkeley County – south
• Clarendon County – west

Major highways

• US 52
• US 378
• US 521
• 
  US 521 Bus.
• SC 41
• 
  SC 41 Bus.
• SC 51
• SC 261
• SC 375
• SC 377
• SC 512
• SC 513
• SC 527
• 
  SC 527 Conn.

Major infrastructure

• Kingstree Station
• Williamsburg Regional Airport

Demographics

2020 census

As of the 2020 census, there were 31,026 people, 12,686 households, and 8,066 families residing in the county.

2010 census

At the 2010 census, there were 34,423 people, 13,007 households, and 8,854 families living in the county. The population density was 36.8 inhabitants per square mile (14.2/km). There were 15,359 housing units at an average density of 16.4 units per square mile (6.3 units/km). The racial makeup of the county was 65.8% black or African American, 31.8% white, 0.4% Asian, 0.3% American Indian, 1.0% from other races, and 0.8% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population. In terms of ancestry, and 4.6% were American.

Of the 13,007 households, 33.2% had children under the age of 18 living with them, 40.0% were married couples living together, 23.0% had a female householder with no husband present, 31.9% were non-families, and 29.0% of all households were made up of individuals. The average household size was 2.53 and the average family size was 3.13. The median age was 40.2 years.

The median income for a household in the county was $24,191 and the median income for a family was $33,705. Males had a median income of $37,678 versus $22,303 for females. The per capita income for the county was $13,513. About 26.5% of families and 32.9% of the population were below the poverty line, including 45.6% of those under age 18 and 27.5% of those age 65 or over.

2000 census

At the 2000 census, there were 37,217 people, 13,714 households, and 10,052 families living in the county. The population density was 40 people per square mile (15 people/km). There were 15,552 housing units at an average density of 17 units per square mile (6.6 units/km). The racial makeup of the county was 66.26% Black or African American, 32.74% White, 0.16% Native American, 0.20% Asian, 0.16% from other races, and 0.48% from two or more races. 0.73% of the population were Hispanic or Latino of any race.

There were 13,714 households, out of which 34.50% had children under the age of 18 living with them, 46.30% were married couples living together, 22.40% had a female householder with no husband present, and 26.70% were non-families. 24.90% of all households were made up of individuals, and 10.40% had someone living alone who was 65 years of age or older. The average household size was 2.69 and the average family size was 3.22.

In the county, the population was spread out, with 28.60% under the age of 18, 9.00% from 18 to 24, 25.70% from 25 to 44, 23.60% from 45 to 64, and 13.00% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 87.90 males. For every 100 females age 18 and over, there were 81.50 males.

The median income for a household in the county was $24,214, and the median income for a family was $30,379. Males had a median income of $26,680 versus $18,202 for females. The per capita income for the county was $12,794. About 23.70% of families and 27.90% of the population were below the poverty line, including 36.10% of those under age 18 and 25.90% of those age 65 or over.

Law and Government

Law enforcement

In 2015, Sheriff Michael Johnson was charged with conspiracy to commit wire fraud, and sentenced to 30 months imprisonment. Johnson, with a co-conspirator, filed false reports of identity theft in order to raise individuals' credit scores, in exchange for up to a thousand dollars in payment.

Politics

Prior to 1948, Williamsburg County was a Democratic Party stronghold similar to the rest of the Solid South, with Democratic presidential candidates receiving near-unanimous margins of victory in most years. The twenty years from 1948 to 1968 were a highly transitional time for the politics of South Carolina & Williamsburg County, largely in part due to the Democratic Party's increasing support for African-American civil rights & enfranchisement. Dixiecrats managed to carry the county twice, while Republicans managed to carry the county three times in this timespan, while increased black registration led to Democrat Hubert Humphrey winning the county in 1968. Since 1968, the majority African-American county has only backed a Republican once in 1972, when Richard Nixon won the county as he swept every county statewide in the midst of a 49-state national landslide.

Economy

In 2022, the GDP was $856 million (about $28,639 per capita), and the real GDP was $703.7 million (about $23,541 per capita) in chained 2017 dollars.

As of April 2024, some of the top employers of the county include United States Department of Justice, Food Lion, Tupperware, and Williamsburg Technical College.

Communities

City

• Kingstree (county seat and largest community)

Towns

• Andrews (mostly in Georgetown County)
• Greeleyville
• Hemingway
• Lane
• Stuckey

Unincorporated communities

See also

• List of counties in South Carolina
• National Register of Historic Places listings in Williamsburg County, South Carolina
• Chaloklowa Chickasaw, state-recognized group that resides in the county