What County Is O'Fallon, Illinois In?
O'Fallon is in St. Clair County, Illinois.
- Official code
- 1755249
- Representative coordinates
- 38.600006, -89.915402
- Land area
- 40.943 km²
- Water area
- 0.284 km²
- State
- Illinois
The representative point identifies this area. It is not a street address or a boundary survey.
County boundaries in O'Fallon
For a point close to the city or county boundary, check the address with the office responsible for your form. Check a point on the county map.
Coordinates of O'Fallon
38.600006, -89.915402 is the Census representative point, not a street address. Convert these coordinates or prepare a map link.
Elevation in O'Fallon
165 m · 541 ft. GNIS archived height at its named reference point (38.5973136, -89.9147301), which may differ from the Census point. Terrain height varies across the place; this is not a city-wide or surveyed elevation. Request height at a different point.
Today’s sunrise and sunset
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Approximate calculations at the representative coordinates, using a level horizon. Terrain and weather can change what you see.
Time zones in O'Fallon
The representative point uses America/Chicago.
| Time zone | Local time and UTC offset | Next clock change |
|---|---|---|
| America/Chicago | UTC-06:00 in January; UTC-05:00 in July. Enable JavaScript for the live clock. | Enable JavaScript for upcoming changes. |
Listed zones overlap the mapped area. A point lookup can distinguish sides of a boundary. Your device’s zone may differ.
Census ZIP areas
These statistical areas overlap the boundary. They are not delivery assignments; confirm mailing details with USPS ZIP Code Lookup.
Areas sharing the mapped boundary
These areas touch this mapped boundary.
Before using this answer on a form
A city boundary, a CDP and a mailing city can mean different things.
Find the county at your current point, check its ZIP area, or find its physical time zone.
Small boundary contacts to check
These maps have small contacts that do not confidently establish another jurisdiction or clock zone. They remain separate from the main answer. Check a precise address near the line with the responsible authority.