According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. Most of the western three-quarters of Lee County is located in the Kinchafoonee-Muckalee sub-basin of the ACF River Basin. The eastern quarter of the county is located in the MiddleFlint River sub-basin of the same ACF River Basin, while a very small corner in the south of Lee County is located in the Lower Flint River sub-basin of the same larger ACF River Basin. An even smaller southwestern corner is located in the Ichawaynochaway Creek sub-basin of the ACF River Basin.
As of the census of 2000, there were 24,757 people, 8,229 households, and 6,797 families living in the county. The population density was 70 people per square mile. There were 8,813 housing units at an average density of 25 per square mile. The racial makeup of the county was 82.24% White, 15.50% Black or African American, 0.24% Native American, 0.84% Asian, 0.01% Pacific Islander, 0.48% from other races, and 0.68% from two or more races. 1.21% of the population were Hispanic or Latino of any race. There were 8,229 households out of which 48.30% had children under the age of 18 living with them, 65.80% were married couplesliving together, 13.00% had a female householder with no husband present, and 17.40% were non-families. 14.30% of all households were made up of individuals and 4.30% had someone living alone who was 65 years of age or older. The average household size was 2.91 and the average family size was 3.21. In the county, the population was spread out with 30.70% under the age of 18, 8.50% from 18 to 24, 33.20% from 25 to 44, 21.30% from 45 to 64, and 6.30% who were 65 years of age or older. The median age was 33 years. For every 100 females, there were 102.10 males. For every 100 females age 18 and over, there were 100.20 males. The median income for a household in the county was $48,600, and the median income for a family was $53,132. Males had a median income of $39,848 versus $25,715 for females. The per capita income for the county was $19,897. About 6.50% of families and 8.20% of the population were below the poverty line, including 10.50% of those under age 18 and 11.70% of those age 65 or over.
2010 census
As of the 2010 United States Census, there were 28,298 people, 9,706 households, and 7,740 families living in the county. The population density was. There were 10,276 housing units at an average density of. The racial makeup of the county was 76.9% white, 18.6% black or African American, 2.2% Asian, 0.3% American Indian, 0.1% Pacific islander, 0.6% from other races, and 1.4% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population. In terms of ancestry, 15.1% were American, 12.3% were Irish, 10.3% were German, and 9.1% were English. Of the 9,706 households, 44.4% had children under the age of 18 living with them, 62.1% were married couples living together, 13.6% had a female householder with no husband present, 20.3% were non-families, and 16.4% of all households were made up of individuals. The average household size was 2.83 and the average family size was 3.17. The median age was 36.0 years. The median income for a household in the county was $59,811 and the median income for a family was $67,943. Males had a median income of $49,213 versus $34,880 for females. The per capita income for the county was $23,867. About 7.5% of families and 8.2% of the population were below the poverty line, including 9.2% of those under age 18 and 8.2% of those age 65 or over.
Historically, Lee County was party of the solidly Democratic Solid South where control of the dominant black population dictated unified white voting for Democratic candidates due to the Republican association with Reconstruction and black political power. However, with a combination of the Great Migration and white in-migration, the black share of the county's population has declined and it is now powerfully Republican, having voted Republican in every presidential election since 1964, with the exception of 1968 and 1976 when it backed Southern “favorite sons” George Wallace and Jimmy Carter.
