THE ST. CLAIR COUNTY LAND BRIEF
Land in the
Southern Illinoian Till Plain setting.
St. Clair County has 657.7 square miles of land in Illinois. 4 mapped landscape regions meet across St. Clair County: Southern Illinoian Till Plain, Middle Mississippi Alluvial Plain, River Hills, among others.
Broad terraced river valleys contrast with wooded slopes and dissected glacial plains. Bottomland settings and upland oak landscapes occur close together across the Interior River Valleys and Hills.
Regional context: Interior River Valleys and Hills ↗ · Regional mapping across the county footprint
Where the landscape changes
St. Clair County intersects 4 mapped regional units. The largest mapped shares are:
- Southern Illinoian Till Plain79.6%
- Middle Mississippi Alluvial Plain11.2%
- River Hills5.6%
- Karstic Northern Ozarkian River Bluffs3.6%
Finding your parcel within St. Clair County
The atlas lists 55 cities, towns, townships, and Census communities associated with St. Clair County, including Millstadt, Fayetteville, Mascoutah. The list includes overlapping geography types and does not divide the county into exclusive service areas.
St. Clair County by land and water
The Census records 16.1 square miles of water within St. Clair County, or 2.4% of its total area. That share is close to St. Clair County’s 2.4%. This is geographic context; waterfront status and usable land must be checked at the parcel.
For scale, St. Clair County has 96.4 times the land area of nearby Freeburg village (6.82 square miles). These areas describe boundaries, not comparable property prices.
The Census boundary meets Clinton County, Madison County, Monroe County, Randolph County, Washington County within Illinois. A tract near one of these lines should be matched to the county identifier on its own records.