St. Clair County, Illinois
St. Clair County, Illinois, has 250,708 residents (July 2025 estimate). Its county seat is Belleville. It uses Central Time and covers 658 sq mi (1,704 km²) of land.
- Resident population, July 2025
- 250,708
- Land area
- 658 sq mi (1,704 km²)
- County seat or government
- Belleville
- Time zone
- Central TimeUTC-06:00 in January; UTC-05:00 in July
- Median household income
- $73,854 ± $1,990
- Median home value
- $180,300 ± $5,056
- Median rent, with utilities
- $1,090 ± $22
- Homes lived in by their owners
- 68.4% ± 1.0 points
- County type
- County
- Metro or micro area
- St. Louis, MO-IL metro areaCentral county
- Water area
- 16.1 sq mi (41.8 km²)
- State
- Illinois
- County code (FIPS)
- 17163
- Coordinates (central point)
- 38.470198, -89.928546
These coordinates mark a central point for the area, not a street address. Income, home value, rent and homes lived in by their owners: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, ± margin at 90% confidence; checked on October 13, 2026.
Time zones in St. Clair County
| Time zone | Local time and UTC offset | Next clock change |
|---|---|---|
| Central TimeAmerica/Chicago | UTC-06:00 in January; UTC-05:00 in July. Enable JavaScript for the live clock. | Enable JavaScript for upcoming changes. |
Near a time-zone line, check where you are with the time-zone finder. Your phone’s setting can differ.
ZIP Code areas, largest first
- 6226935,923 people
- 6223431,648 people
- 6222129,875 people
- 6222628,255 people
- 6222019,152 people
- 6229818,208 people
- 6220816,821 people
- 6222316,269 people
- 6229415,325 people
- 6223614,154 people
- 6220612,959 people
- 6225810,437 people
All 34
- 622327,063 people
- 622076,984 people
- 622546,710 people
- 622606,668 people
- 622056,459 people
- 622436,418 people
- 622035,465 people
- 622255,242 people
- 622014,921 people
- 622654,555 people
- 622934,433 people
- 622854,239 people
- 622394,232 people
- 622044,055 people
- 620603,558 people
- 622643,097 people
- 622572,046 people
- 622401,796 people
- 622551,092 people
- 62059729 people
- 62282563 people
- 62289273 people
34 ZIP Code areas overlap St. Clair County. People counts are 2020–2024 estimates for each whole ZIP area. Mailing ZIPs can differ; check an address with USPS ZIP Code Lookup.
Official county information
We don’t have a website for this county yet. The US government’s local-office directory ↗ lists its offices. A geographic lookup cannot determine eligibility, tax liability or a court obligation.
Townships in St. Clair County, largest first
- St. Clair Township35,601 people
- Caseyville Township35,032 people
- O'Fallon Township26,785 people
- Centreville Township19,674 people
- East St. Louis Township17,999 people
- Shiloh Valley Township12,849 people
- Mascoutah Township9,512 people
- Stookey Township9,018 people
- Canteen Township7,877 people
- Sugar Loaf Township6,779 people
- Millstadt Township6,616 people
- Freeburg Township5,006 people
All 21
- Lebanon Township4,369 people
- Smithton Township4,102 people
- New Athens Township2,633 people
- Prairie Du Long Township2,607 people
- Marissa Township1,835 people
- Fayetteville Township1,600 people
- Lenzburg Township943 people
- Engelmann Township758 people
- Stites Township729 people
People counts are American Community Survey 2020–2024 5-year estimates. All townships in Illinois, by county
School districts in St. Clair County, largest first
- Belleville Township High School District 201104,251 people
- Collinsville Community Unit School District 1047,304 people
- O'Fallon Township High School District 20344,393 people
- Belleville School District 11835,305 people
- O'Fallon Community Consolidated School District 9032,272 people
- East St. Louis School District 18925,236 people
- Mascoutah Community Unit School District 1920,347 people
- Waterloo Community Unit School District 519,409 people
- Cahokia Community Unit School District 18715,292 people
- Whiteside School District 11513,613 people
- Columbia Community Unit School District 413,590 people
- Freeburg Community High School District 7713,462 people
All 31
- Harmony Emge School District 17510,594 people
- Wolf Branch School District 1139,159 people
- Freeburg Community Consolidated School District 708,502 people
- Millstadt Consolidated Community School District 1608,179 people
- Wesclin Community Unit School District 37,837 people
- Belle Valley School District 1197,509 people
- Pontiac-William Holliday School District 1057,483 people
- Grant Community Consolidated School District 1107,132 people
- Central School District 1046,441 people
- Dupo Community Unit School District 1966,246 people
- Lebanon Community Unit School District 95,569 people
- Shiloh Village School District 854,969 people
- Smithton Community Consolidated School District 1304,079 people
- New Athens Community Unit School District 603,764 people
- High Mount School District 1163,253 people
- Signal Hill School District 1812,814 people
- Marissa Community Unit School District 402,354 people
- St. Libory Consolidated School District 30802 people
- Brooklyn Community Unit School District 188729 people
Districts with land in the county; a district can cross county lines. People counts are American Community Survey 2020–2024 5-year estimates. A district boundary doesn’t decide which school a student attends.
Cities, towns and communities, largest first
These areas overlap the mapped boundary; an overlap does not mean that every address belongs to both.
- Belleville, Illinois (city)41,370 people
- O'Fallon, Illinois (city)32,262 people
- Collinsville, Illinois (city)24,031 people
- East St. Louis, Illinois (city)17,999 people
- Cahokia Heights, Illinois (city)17,106 people
- Fairview Heights, Illinois (city)16,745 people
- Swansea, Illinois (village)14,710 people
- Shiloh, Illinois (village)14,572 people
- Columbia, Illinois (city)11,127 people
- Mascoutah, Illinois (city)8,816 people
- Freeburg, Illinois (village)4,592 people
- Lebanon, Illinois (city)4,474 people
All 35
- Caseyville, Illinois (village)4,130 people
- Millstadt, Illinois (village)4,008 people
- Scott AFB, Illinois (CDP)3,957 people
- Dupo, Illinois (village)3,879 people
- Smithton, Illinois (village)3,680 people
- New Baden, Illinois (village)3,463 people
- Madison, Illinois (city)2,900 people
- Fairmont City, Illinois (village)2,492 people
- New Athens, Illinois (village)1,933 people
- Washington Park, Illinois (village)1,701 people
- Marissa, Illinois (village)1,232 people
- Brooklyn, Illinois (village)729 people
- St. Libory, Illinois (village)559 people
- Hecker, Illinois (village)521 people
- Lenzburg, Illinois (village)428 people
- Fayetteville, Illinois (village)357 people
- Sauget, Illinois (village)307 people
- Summerfield, Illinois (village)248 people
See all 35 cities, towns and communities in St. Clair County, largest first
Bordering areas, nearest first
Distances are straight lines between map points.
- Monroe County, Illinois19 mi southwest
- St. Louis city, Missouri21 mi northwest
- Madison County, Illinois25 mi north
- Clinton County, Illinois29 mi east
- Washington County, Illinois29 mi east
- Randolph County, Illinois29 mi south
- St. Louis County, Missouri30 mi northwest
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