O'Fallon city, Illinois
Official LSAD Designation: O'Fallon city • Census GEOID: 1755249
• St. Clair County
O'Fallon city is an incorporated city in St. Clair County, Illinois. According to official records from the Census (2025), O'Fallon city had an estimated population of 32,656 residents. Official Census Bureau geographic records classify this community under LSAD designation O'Fallon city (GEOID 1755249).
Local Government Administration U.S. Census Bureau GMAF
City Of O Fallon
Municipal
Official Title:
City Administrator
Address:
255 S LINCOLN AVE, O FALLON IL 62269-2139
County Of St Clair
County
Official Title:
Auditor
Address:
10 PUBLIC SQ, BELLEVILLE IL 62220-1623
Civic & Statistical Snapshot
| Category | Estimate | Survey Period / Source |
|---|---|---|
| Total Population | 32,656 | 2025 |
| Median Household Income | $105,982 | 2020-2024 |
| Median Home Value | $295,700 | 2020-2024 |
| Land Area | 16.04 sq mi | Gazetteer (2026) |
| Civic & Public Services | Hospitals, Libraries, Colleges | CMS / IMLS / IPEDS |
| Schools & Districts | NCES Directory Listings | Provided by k12guides.com |
| Nearby Airports | Landing Facilities | Provided by airport-data.com |
| Climate & Weather | NOAA 30-Year Normals | 1991–2020 |
Source: U.S. Census Bureau (PEP, ACS 5-Year).