Named for Revolutionary War general, Arthur St. Clair. St. Clair County was created from Shelby County on 20 November, 1818. On 20 December, 1820, a part of the county was added to Jefferson. The county seat is located in both Ashville on the north side of the mountain, and Pell City on the south side of the mountain. Ashville holds the county archives, the wills & probates, marriages, and the old newspapers.