Allendale County, South Carolina  Allendale County is a county in the U.S. state of South Carolina. As of the 2018 census estimates, the population was 8,903  making it the least populous county in South Carolina. Its county seat is Allendale. Allendale County was formed in 1919 from southwestern portions of Barnwell County, along the Savannah River. It is the location of the Topper Site, an archeological excavation providing possible evidence of a pre-Clovis culture dating back 50,000 years. The site is near a source of chert on private land in Martin owned by Clariant Corporation, a Swiss chemical company with a plant there. The site, named after John Topper, a local resident who discovered it, has been under excavation by archeologists from the University of South Carolina for about one month a year since 1999, after an initial exploratory dig in the mid-1980s. According to the U.S. Census Bureau, the county has a total area of , of which is land and (1.0%) is water. The Savannah River forms the county's western border with Georgia. Allendale is 62 miles from Augusta, Georgia; 73 miles from Savannah, Georgia; 87 miles from Columbia; and 90 miles from Charleston. Before interstate highways were built, Allendale had several motels, primarily serving travelers going between Northeastern states and Florida. Traffic that formerly traveled U.S. 301 through Allendale now uses Interstate-95. At the 2000 census there were 11,211 people, 3,915 households and 2,615 families living in the county. The population density was 28 people per square mile (11/km²). There were 4,568 housing units at an average density of 11 per square mile (4/km²). The racial makeup of the county was 71.0 percent Black or African American, 27.37 percent White, 0.12 percent Asian, 0.09 percent Native American, 0.06 percent Pacific Islander, 0.85 percent from other races, and 0.51 percent from two or more races. 1.61 percent of the population were Hispanic or Latino of any race. Of the 3,915 households 30.3 percent had children under the age of 18 living with them, 35.8 percent were married couples living together, 25.8 percent had a female householder with no husband present, and 33.2 percent were non-families. 30.0 percent of all households were one person and 12.3 percent had someone living alone who was 65 or older.