St. Clair County, Alabama: History
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.
Due to the relatively high terrain of the far southern end of the Appalachian Mountains which divides the county in a northeast–southwest orientation, and the difficulty of communication and administration from either side of the county to the other, a second county seat was established in Pell City to better provide administration and services to the southeast side of the county.
In 2019, St. Clair County became the seventh county in Alabama to adopt its own flag.