Its name is in honor of General Arthur St. Clair, an officer in the French and Indian War.

[1] St. Clair County is included in the Birmingham, Alabama Metropolitan Statistical Area.

[1][4] The county seat was incorporated and named "Ashville" in honor of John Ash.

As of the census of 2010, there were 83,593 people, 31,624 households, and 23,364 families living in the county.

As of the census of 2000, there were 64,742 people, 24,143 households, and 18,445 families living in the county.

[17] 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.

St. Clair County is home to Logan Martin Lake.

It also contains Horse Pens 40, a private outdoor park on top of Chandler Mountain.

Historically, the Southern Railway ran several daily passenger trains, including the Kansas City-Florida Special and an Atlanta-Birmingham section of the Piedmont Limited, making stops in Pell City.

[20][21] Today, the nearest passenger service is Amtrak's Crescent in Anniston, 30.6 miles to the east.