St. Clair County

St. Clair County is an administrative division in Illinois that spans across a mix of communities, farmland, and developed areas. The county includes several towns and villages connected by highways and local roads that form its basic infrastructure.

The county was established in 1818 as a separate administrative region during the early territorial expansion of Illinois. Its growth reflected the pattern of settlement and development that characterized the broader frontier period of the American Midwest.

The population of St. Clair County represents diverse backgrounds, with 82.28% White, 9.46% Black or African American, and 4.16% mixed-race residents.

The area is accessible by major highways and state routes that connect the county to surrounding regions. Visitors should plan for travel times between communities as they are spread across the county rather than concentrated in one location.

Logan Martin Lake within St. Clair County provides fishing opportunities, while Horse Pens 40 park displays natural rock formations on Chandler Mountain.

Location: Illinois

Inception: April 27, 1790

Capital city: Belleville

Shares border with: Madison County, Randolph County, Monroe County, Clinton County, Washington County, St. Louis County, St. Louis

Website: http://co.st-clair.il.us

GPS coordinates: 38.47000,-89.93000

Latest update: December 14, 2025 18:15