County · Illinois
St. Clair County, Illinois
St. Clair County, Illinois. St. Clair County had 250,708 residents in 2025 by the Census Bureau's estimate, down 2.7% since 2020, a steeper fall than Illinois's (−0.8%). It holds 54 places (30 cities, villages and boroughs, 19 towns and townships and 5 census-designated) and 68 census tracts. GEOID 17163.
St. Clair County is one of the 15 counties of the St. Louis, MO-IL metropolitan statistical area (the Census Bureau's July 2023 delineation).
Residents, July 2025 estimate
250,708
Census Bureau estimate (no margin published)
2020 Census count: 257,400 · ACS 2020-2024: 253,694
Median household income
$73,854
±$1,990 (90% margin)
Illinois: $83,390
Median home value
$180,300
±$5,056 (90% margin)
Illinois: $263,300
Median gross rent
$1,090
±$22 (90% margin)
Illinois: $1,274
How many people live in St. Clair County, and is it growing?
The 2020 Census counted 257,400 residents in St. Clair County. The Census Bureau estimates 250,708 for July 1, 2025, down 2.7% since 2020, a steeper fall than Illinois's (−0.8%). The 2020-2024 American Community Survey puts the population at 253,694 over 658 square miles of land.
| Measure | St. Clair County | Illinois | Change since 2015-2019 |
|---|---|---|---|
| Total population | 253,694 | 12,694,798 | −8,644 |
| Households | 100,846±1,013 | 5,036,449 | −3,259 |
| Average household size | 2.47±0.02 | 2.46 | no clear change |
| Housing units | 115,630±82 | 5,457,452 | −4,606 |
St. Clair County's population since 2000
From 256,082 in 2000 to 250,708 in 2025: down 2.1%. The 2000, 2010 and 2020 figures are census counts. The 2005 figure is the Census Bureau's intercensal estimate, revised to fit the 2000 and 2010 counts and drawn on 2010 boundaries; 2015 and 2025 are July 1 estimates made from the census before them.
Source: The 2000, 2010 and 2020 Census counts and the Census Bureau's population estimates (intercensal 2000-2010, Vintage 2020, Vintage 2025) · Census population estimates
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026); PEP Vintage 2025 (CO-EST2025); 2020 Census · Check it at data.census.gov
What cities and towns are in St. Clair County?
St. Clair County holds 54 places: 30 cities, villages and boroughs (incorporated places), 19 towns and townships (county subdivisions with their own government) and 5 census-designated places. The largest is Belleville with 40,237 residents (2025 estimate). Places that cross a county line are listed with the share of their 2020 residents who live in this county.
| Belleville | 42,404 | $63,535 |
|---|---|---|
| St. Clair Township | 35,758 | $80,309 |
| Caseyville Township | 35,580 | $87,204 |
| O'Fallon | 32,289 | $105,982 |
| O'Fallon Township | 26,291 | $100,136 |
| Centreville Township | 20,213 | $34,675 |
| East St. Louis | 18,469 | $35,700 |
| Cahokia Heights | – | $33,792 |
| Fairview Heights | 16,706 | $80,930 |
| Swansea | 14,386 | $91,587 |
| Shiloh | 14,098 | $99,573 |
| Shiloh Valley Township | 12,824 | $104,772 |
| Mascoutah Township | 9,433 | $98,125 |
| Stookey Township | 9,219 | $81,894 |
| Mascoutah | 8,754 | $97,375 |
| Canteen Township | 8,004 | $49,755 |
| Sugar Loaf Township | 6,931 | $72,985 |
| Millstadt Township | 6,756 | $91,144 |
| Freeburg Township | 5,065 | $91,563 |
| Lebanon Township | 4,933 | $89,615 |
| Lebanon | 4,691 | $88,750 |
| Freeburg | 4,582 | $92,065 |
| Caseyville | 4,400 | $60,669 |
| Smithton Township | 4,174 | $122,778 |
| Millstadt | 4,071 | $90,901 |
| Smithton | 4,006 | $135,455 |
| Dupo | 3,996 | $61,644 |
| Scott AFBGEOID 1768328 | 3,688 | $103,390 |
| Collinsville | 24,366 | $67,612 |
| Prairie Du Long TownshipGEOID 1716361600 | 2,622 | $159,129 |
| Washington Park | 2,592 | $38,750 |
| New Athens Township | 2,562 | $51,786 |
| Marissa Township | 2,260 | $68,250 |
| Fairmont City | 2,265 | $48,147 |
| New Athens | 1,955 | $56,553 |
| Marissa | 1,833 | $54,814 |
| Fayetteville Township | 1,535 | $100,858 |
| Lenzburg Township | 958 | $52,917 |
| Engelmann TownshipGEOID 1716324205 | 758 | $143,333 |
| Brooklyn | 649 | $30,673 |
| St. Libory | 628 | $116,964 |
| Lenzburg | 468 | $42,656 |
| East Carondelet | 390 | $67,500 |
| Summerfield | 347 | $51,944 |
| FayettevilleGEOID 1725713 | 302 | $59,583 |
| New Baden | 3,428 | $81,393 |
| Columbia | 10,999 | $107,606 |
| SaugetGEOID 1767756 | 141 | $62,171 |
| DarmstadtGEOID 1718641 | 49 | not published |
| FloravilleGEOID 1726467 | 49 | not published |
| RentchlerGEOID 1763355 | 45 | not published |
| PaderbornGEOID 1757160 | 35 | not published |
| Madison | 3,171 | $49,326 |
| Hecker | 429 | $79,583 |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026); 2020 place-by-county parts · Check it at data.census.gov
Who lives in St. Clair County?
The median resident of St. Clair County is 39.9 years old; 23.0% are under 18 and 17.3% are 65 or older. The largest group is non-Hispanic white residents at 59.1%, then non-Hispanic Black residents at 27.7%. 3.3% of residents were born outside the United States.
| Measure | St. Clair County | Illinois | Change since 2015-2019 |
|---|---|---|---|
| Median age | 39.9±0.3 | 39.0 | +1.3 |
| Under 18 years | 23.0% | 21.8% | – |
| 65 years and over | 17.3% | 17.0% | – |
| Hispanic or Latino (any race) | 5.1% | 18.8% | +1.0 pts |
| White alone, not Hispanic | 59.1%±0.3 pts | 58.1% | −2.5 pts |
| Black or African American alone, not Hispanic | 27.7%±0.6 pts | 13.3% | −2.1 pts |
| Asian alone, not Hispanic | 1.6%±0.1 pts | 5.9% | no clear change |
| American Indian and Alaska Native alone, not Hispanic | 0.2%±0.1 pts | 0.1% | – |
| Native Hawaiian and Other Pacific Islander alone, not Hispanic | 0.0%±0.1 pts | 0.0% | – |
| Two or more races, not Hispanic | 5.8%±0.7 pts | 3.4% | – |
| Some other race alone, not Hispanic | 0.5%±0.3 pts | 0.4% | – |
| Born outside the United States | 3.3%±0.3 pts | 14.7% | no clear change |
| Speak a language other than English at home (age 5+) | 5.0%±0.4 pts | 24.0% | – |
| Civilian veterans (age 18+) | 11.5%±0.6 pts | 4.8% | – |
| With a disability | 15.2%±0.7 pts | 12.1% | – |
| No health insurance coverage | 5.1%±0.4 pts | 6.9% | −1.1 pts |
| High school graduate or higher (age 25+) | 93.5%±0.6 pts | 90.5% | – |
| Bachelor's degree or higher (age 25+) | 31.8%±0.8 pts | 37.8% | +3.8 pts |
| Graduate or professional degree (age 25+) | 13.8%±0.8 pts | 15.3% | – |
| Moved from another state in the past year | 3.0%±0.4 pts | 1.6% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profiles DP02, DP05) · Check it at data.census.gov
What do households in St. Clair County earn?
Half of St. Clair County's 100,846 households earn less than $73,854 a year (±$1,990), against $83,390 in Illinois. In 2015-2019 the median was $67,908 in 2024 dollars, so it rose by $5,946 after inflation. 13.6% of residents live below the poverty line.
| Measure | St. Clair County | Illinois | Change since 2015-2019 |
|---|---|---|---|
| Median household income | $73,854±$1,990 | $83,390 | +$5,946 |
| Mean household income | $96,049±$1,809 | $115,638 | – |
| Per capita income | $38,942±$708 | $46,406 | no clear change |
| People below the poverty line | 13.6%±0.9 pts | 11.8% | no clear change |
| Children under 18 below the poverty line | 18.9%±2.2 pts | 15.1% | −3.2 pts |
| Households receiving SNAP | 16.2%±0.9 pts | 13.8% | – |
| Households with a broadband subscription | 89.7%±0.9 pts | 90.8% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP03) · Check it at data.census.gov
What does housing cost in St. Clair County?
Owners occupy 68.4% of St. Clair County's occupied homes and renters 31.6%. The median owner-occupied home is valued at $180,300 by its owner (±$5,056). The median renter pays $1,090 a month including utilities, and 39.8% of renters pay 35% or more of their income on rent.
| Measure | St. Clair County | Illinois | Change since 2015-2019 |
|---|---|---|---|
| Median home value (owner-occupied) | $180,300±$5,056 | $263,300 | +$22,771 |
| Median gross rent | $1,090±$22 | $1,274 | +$30 |
| Renters paying 35% or more of income on rent | 39.8%±2.5 pts | 39.0% | no clear change |
| Median monthly owner costs, with a mortgage | $1,645±$31 | $1,987 | – |
| Owner-occupied homes | 68.4%±1.2 pts | 67.1% | +3.2 pts |
| Housing units | 115,630±82 | 5,457,452 | −4,606 |
| Homeowner vacancy rate | 1.1%±0.4 pts | 1.0% | – |
| Rental vacancy rate | 4.7%±1.2 pts | 5.0% | – |
| Single-family detached homes | 72.1%±0.9 pts | 58.2% | – |
| Mobile homes | 4.4%±0.5 pts | 2.3% | – |
| Built 2020 or later | 0.9%±0.2 pts | 0.7% | – |
| Built 1939 or earlier | 13.5%±0.9 pts | 20.2% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP04) · Check it at data.census.gov
How many new homes is St. Clair County building?
Builders took permits for 463 new housing units across St. Clair County in 2025 (285 single-family), 1.8 per 1,000 residents.
Source: Building Permits Survey, annual county files 2019-2025, U.S. Census Bureau · Census Building Permits Survey
How do people in St. Clair County get to work?
75.4% of St. Clair County's workers drive alone and 12.4% work from home. The average trip to work takes 24.0 minutes. The unemployment rate in 2020-2024 averaged 6.0%.
| Measure | St. Clair County | Illinois | Change since 2015-2019 |
|---|---|---|---|
| In the labor force (age 16+) | 63.4%±0.7 pts | 65.0% | – |
| Unemployment rate | 6.0%±0.7 pts | 5.8% | no clear change |
| Drove alone to work | 75.4%±1.2 pts | 65.9% | – |
| Carpooled | 8.1%±0.8 pts | 7.8% | – |
| Public transportation | 1.6%±0.4 pts | 5.8% | – |
| Walked | 1.5%±0.4 pts | 2.8% | – |
| Worked from home | 12.4%±0.9 pts | 15.9% | +8.9 pts |
| Mean travel time to work | 24.0 min±0.6 | 27.8 min | −1.0 min |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP03) · Check it at data.census.gov
What are St. Clair County's census tracts?
St. Clair County is divided into 68 census tracts. Among those with a reliable estimate, median household income runs from $21,942 (Tract 5045.01) to $179,261 (Tract 5043.53).
All 68 census tracts of St. Clair County, with their figures
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) · Check it at data.census.gov
How does St. Clair County compare with Illinois's other counties?
| Measure | Rank |
|---|---|
| Population | 9th of 102 |
| Growth 2020-2025 | 62nd of 102 |
| Residents per square mile | 9th of 102 |
| Median household income | 29th of 102 |
| Median home value | 23rd of 102 |
| Median gross rent | 10th of 102 |
| Poverty rate | 39th of 102 |
| Bachelor's degree or higher | 17th of 102 |
| Median age | 82nd of 102 |
Source: PlainCities ranks from the American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) and PEP Vintage 2025 · How ranks are computed
How these figures are made: methodology and release checks · reading a margin of error · every state · corrections
Not on this page: crime, weather and schools for St. Clair County are other agencies' records. Crime: the FBI's Crime Data Explorer · climate: NOAA's U.S. Climate Normals · schools: the National Center for Education Statistics' school search.