As of the census of 2000, there were 20,949 people, 8,086 households, and 5,789 families residing in the county. The population density was 24 people per square mile (9/km²). There were 9,520 housing units at an average density of 11 per square mile (4/km²). The racial makeup of the county was 55.95% White, 42.96% Black or African American, 0.12% Native American, 0.11% Asian, 0.02% Pacific Islander, 0.22% from other races, and 0.63% from two or more races. About 0.70% of the population were Hispanic or Latino.
There were 8,086 households, out of which 32.60% had children under the age of 18 living with them, 49.80% were married couples living together, 18.20% had a female householder with no husband present, and 28.40% were non-families. Nearly 26.40% of all households were made up of individuals, and 12.50% had someone living alone who was 65 years of age or older. The average household size was 2.56, and the average family size was 3.11.
In the county, the population was spread out with 27.30% under the age of 18, 8.50% from 18 to 24, 25.80% from 25 to 44, 22.80% from 45 to 64, and 15.70% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 88.10 males. For every 100 females age 18 and over, there were 83.30 males.
The median income for a household in the county was $26,254, and the median income for a family was $32,938. Males had a median income of $28,843 versus $20,569 for females. The per capita income for the county was $13,746. About 20.10% of families and 24.90% of the population were below the poverty line, including 34.30% of those under age 18 and 22.30% of those age 65 or over.