THE MERCER COUNTY LAND BRIEF
Land in the
Western Dissected Illinoian Till Plain setting.
Mercer County has 561.2 square miles of land in Illinois. 4 mapped landscape regions meet across Mercer County: Western Dissected Illinoian Till Plain, Upper 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
Mercer County intersects 4 mapped regional units. The largest mapped shares are:
- Western Dissected Illinoian Till Plain70.8%
- Upper Mississippi Alluvial Plain17.7%
- River Hills7.2%
- Illinois/Indiana Prairies4.3%
Central Corn Belt Plains in Mercer County
Glaciated plains historically supported tallgrass prairie mixed with oak and hickory woodland. Dark prairie soils and broad farming landscapes distinguish much of the Central Corn Belt.
Read the regional source ↗Finding your parcel within Mercer County
The atlas lists 33 cities, towns, townships, and Census communities associated with Mercer County, including Eliza, New Boston, Suez. The list includes overlapping geography types and does not divide the county into exclusive service areas.
Mercer County by land and water
The Census records 7.5 square miles of water within Mercer County, or 1.3% of its total area. That share is close to Mercer County’s 1.3%. This is geographic context; waterfront status and usable land must be checked at the parcel.
For scale, Mercer County has 239.4 times the land area of nearby Aledo city (2.34 square miles). These areas describe boundaries, not comparable property prices.
The Census boundary meets Henderson County, Henry County, Knox County, Rock Island County, Warren County within Illinois. A tract near one of these lines should be matched to the county identifier on its own records.

