St. Clair County, Illinois
St. Clair County profile, demographic data, and geographic information.
St. Clair County is a county located in Illinois, United States of America. As of official census estimates, it has a reported population of 250,708. The land area covers 657.75 sq mi. [1]
Local Government Administration U.S. Census Bureau GMAF
County Of St Clair
County
Official Title:
Auditor
Address:
10 PUBLIC SQ, BELLEVILLE IL 62220-1623
Demographics & Population
| Demographic Metric | Estimate / Count | Margin of Error | Survey Period / Source |
|---|---|---|---|
| Total Population (2025 PEP Estimate) | 250,708 | — | 2025 / Census |
| Median Age | 39.9 yrs | ±0.3 | 2020-2024 / Census ACS 5-Year 2024 |
| Total Households | 100,846 | ±1,013 | 2020-2024 / Census ACS 5-Year 2024 |
Source: U.S. Census Bureau (PEP, ACS 5-Year).
Housing & Real Estate Profile
| Housing Metric | Estimate / Value | Margin of Error |
|---|---|---|
| Total Housing Units | 115,630 | ±82 |
| Occupied Housing Units | 100,846 | ±1,013 |
| Vacant Housing Units | 14,784 | ±1,032 |
| Median Home Value | $180,300 | ±$5,056 |
| Median Gross Rent | $1,090 | ±$22 |
Source: U.S. Census Bureau ACS 5-Year (2020-2024).
Economy & Workforce
| Economic Metric | Estimate / Value | Margin of Error |
|---|---|---|
| Median Household Income | $73,854 | ±$1,990 |
| Per Capita Income | $38,942 | ±$708 |
| Poverty Rate | 13.6% | ±0.9% |
| Population Below Poverty Level | 33,710 | ±2,344 |
| Unemployment Rate | 6% | ±0.7% |
| Civilian Labor Force, Employed | 116,728 | ±1,531 |
| Broadband Internet Rate | 89.7% | ±1% |
Source: U.S. Census Bureau ACS 5-Year (2020-2024).
Climate & Weather Observations
NOAA Monthly Climate Normals
Observation Station: Climate data reflects NOAA 1991–2020 standard normals recorded at BELLEVILLE SIU RSCH, IL US, located 5.6 miles from St. Clair County. Local microclimates, topography, and elevation may cause municipal conditions to differ.
| Month | High (°F) | Low (°F) | Mean (°F) | Precip (in) | Snow (in) |
|---|---|---|---|---|---|
| January | 42.9° | 24.3° | 33.6° | 2.56" | 3.4" |
| February | 48.6° | 28.0° | 38.3° | 2.16" | 3.3" |
| March | 59.2° | 36.3° | 47.8° | 3.44" | 1.0" |
| April | 70.6° | 46.0° | 58.3° | 4.90" | 0.0" |
| May | 79.1° | 56.3° | 67.7° | 5.05" | 0.0" |
| June | 87.3° | 64.5° | 75.9° | 4.62" | 0.0" |
| July | 90.2° | 67.8° | 79.0° | 4.03" | 0.0" |
| August | 89.1° | 65.3° | 77.2° | 3.92" | 0.0" |
| September | 83.3° | 56.9° | 70.1° | 3.35" | 0.0" |
| October | 72.6° | 46.7° | 59.7° | 3.12" | 0.0" |
| November | 58.1° | 36.9° | 47.5° | 3.60" | 0.6" |
| December | 46.3° | 28.3° | 37.3° | 2.61" | 2.9" |
Source: NOAA U.S. Climate Normals (1991–2020).
Local Weather Forecast
Weather forecast data is currently unavailable in the local cache.
Sources & Data Provenance
- Geographic Classification & Identifiers: U.S. Census Bureau Gazetteer (2026) and TIGER/Line Shapefiles. GEOID: 17163. • Official Source Dataset →
- Socioeconomic & Housing Metrics: U.S. Census Bureau American Community Survey (ACS) 5-year estimates and Population Estimates Program (PEP). Margin of Error (MOE) intervals are reported where published; suppressed values are never estimated or replaced with false zeros.
- Civic Directory Datasets: Centers for Medicare & Medicaid Services (CMS Hospital Directory), National Center for Education Statistics (NCES IPEDS Postsecondary Directory), and Institute of Museum and Library Services (IMLS Public Libraries Survey). Airport landing facilities are provided by airport-data.com.
- Weather & Climate Observations: National Oceanic and Atmospheric Administration (NOAA) U.S. Climate Normals 1991–2020 and National Weather Service (NWS) point forecasts.