St. Clair County was established on November 20, 1818 by the Alabama Territory legislature by splitting the area from Shelby County. The county seat was incorporated and named "Ashville" in honor of John Ash. In 1836, a portion of St. Clair County was separated to establish Cherokee County and DeKalb County. In 1866, after the Civil War, a northeast section of the county was used to create Etowah County.
Geography
According to the U.S. Census Bureau, the county has a total area of, of which is land and is water.
At the 2000 census there were 64,742 people, 24,143 households, and 18,445 families living in the county. The population density was 102 people per square mile. There were 27,303 housing units at an average density of 43 per square mile. The racial makeup of the county was 90.03% White, 8.13% Black or African American, 0.37% Native American, 0.17% Asian, 0.03% Pacific Islander, 0.41% from other races, and 0.85% from two or more races. 1.06% of the population were Hispanic or Latino of any race. In 2000 the largest ancestry groups in St. Clair county were:
Of the 24,143 households 35.10% had children under the age of 18 living with them, 62.80% were married couples living together, 10.00% had a female householder with no husband present, and 23.60% were non-families. 20.80% of households were one person and 8.20% were one person aged 65 or older. The average household size was 2.60 and the average family size was 3.01. The age distribution was 25.40% under the age of 18, 7.90% from 18 to 24, 30.70% from 25 to 44, 24.30% from 45 to 64, and 11.70% 65 or older. The median age was 36 years. For every 100 females, there were 101.80 males. For every 100 females age 18 and over, there were 98.80 males. The median household income was $37,285 and the median family income was $43,152. Males had a median income of $33,914 versus $24,433 for females. The per capita income for the county was $17,960. About 9.60% of families and 12.10% of the population were below the poverty line, including 15.20% of those under age 18 and 12.60% of those age 65 or over.
2010 census
At the 2010 census there were 83,593 people, 31,624 households, and 23,364 families living in the county. The population density was 132 people per square mile. There were 35,541 housing units at an average density of 56 per square mile. The racial makeup of the county was 88.2% White, 8.6% Black or African American, 0.3% Native American, 0.6% Asian, 0.1% Pacific Islander, 0.9% from other races, and 1.3% from two or more races. 2.1% of the population were Hispanic or Latino of any race. Of the 31,624 households 30.7% had children under the age of 18 living with them, 58.3% were married couples living together, 11.2% had a female householder with no husband present, and 26.1% were non-families. 22.5% of households were one person and 8.5% were one person aged 65 or older. The average household size was 2.58 and the average family size was 3.02. The age distribution was 23.7% under the age of 18, 7.8% from 18 to 24, 27.8% from 25 to 44, 27.6% from 45 to 64, and 13.1% 65 or older. The median age was 38.6 years. For every 100 females, there were 100.5 males. For every 100 females age 18 and over, there were 102.3 males. The median household income was $48,837 and the median family income was $56,107. Males had a median income of $43,287 versus $32,843 for females. The per capita income for the county was $22,192. About 8.3% of families and 10.6% of the population were below the poverty line, including 13.2% of those under age 18 and 9.5% of those age 65 or over.
