According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. The north-to-northeastern quarter of Warren County, north of a line between the county's northwestern corner, Norwood, and Camak, is located in the Little River sub-basin of the Savannah River basin. The southeastern quarter, from Camak in the north, and bordered by a northwest-to-southeast line running through Warrenton, is located in the Brier Creek sub-basin of the larger Savannah River basin. The western half of the county, west of Warrenton, is located in the Upper Ogeechee River sub-basin of the Ogeechee River basin.
As of the 2010 United States Census, there were 5,834 people, 2,315 households, and 1,582 families living in the county. The population density was. There were 2,985 housing units at an average density of. The racial makeup of the county was 61.7% black or African American, 36.9% white, 0.4% Asian, 0.2% American Indian, 0.2% from other races, and 0.6% from two or more races. Those of Hispanic or Latino origin made up 0.9% of the population. In terms of ancestry, 33.5% were American, and 6.3% were English. Of the 2,315 households, 30.6% had children under the age of 18 living with them, 40.5% were married couplesliving together, 23.4% had a female householder with no husband present, 31.7% were non-families, and 28.3% of all households were made up of individuals. The average household size was 2.48 and the average family size was 3.05. The median age was 42.9 years. The median income for a household in the county was $31,043 and the median income for a family was $36,925. Males had a median income of $33,349 versus $21,884 for females. The per capita income for the county was $15,987. About 20.5% of families and 25.7% of the population were below the poverty line, including 39.4% of those under age 18 and 22.0% of those age 65 or over.
2000 census
As of the census of 2000, there were 6,336 people, 2,435 households, and 1,692 families living in the county. The population density was 22 people per square mile. There were 2,767 housing units at an average density of 10 per square mile. The racial makeup of the county was 59.47% Black or African American, 39.46% White, 0.17% Native American, 0.14% Asian, 0.30% from other races, and 0.46% from two or more races. 0.80% of the population were Hispanic or Latino of any race. There were 2,435 households out of which 30.60% had children under the age of 18 living with them, 42.10% were married couples living together, 22.10% had a female householder with no husband present, and 30.50% were non-families. 27.40% of all households were made up of individuals and 12.60% had someone living alone who was 65 years of age or older. The average household size was 2.55 and the average family size was 3.09. In the county, the population was spread out with 26.40% under the age of 18, 8.70% from 18 to 24, 25.50% from 25 to 44, 23.40% from 45 to 64, and 16.10% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 86.40 males. For every 100 females age 18 and over, there were 79.90 males. The median income for a household in the county was $27,366, and the median income for a family was $32,868. Males had a median income of $28,177 versus $20,082 for females. The per capita income for the county was $14,022. About 24.10% of families and 27.00% of the population were below the poverty line, including 36.00% of those under age 18 and 27.50% of those age 65 or over.
