St. Clair County: Demographics & People
Census counts 253,694 people in St. Clair County. Median age 39.9 years. (0.8y older than Illinois). Population is 28% Black and 5% Hispanic or Latino. County is losing 2,121 residents per year (2022-2023). County health: 44% adult obesity, 16% smoke.
Population & Trend
Current population 253,694; figures track the most recent Census ACS 5-year estimates.
| Population | 253,694 people |
|---|---|
| Total Town Population | 199,921 people |
Age Distribution
Median age 39.9y is 1.0 years older than the U.S. median (38.9y).
| Age Summary · Total Pop | 253,694 |
|---|---|
| Age Summary · Under 18 | 58,413 |
| Age Summary · 18 To 34 | 52,758.0× |
| Age Summary · 35 To 64 | 98,516.0× |
| Age Summary · 65 Plus | 44,007 |
| Age Summary · Pct Under 18 | 23.0% |
| Age Summary · Pct 18 To 34 | 20.8% |
| Age Summary · Pct 35 To 64 | 38.8% |
| Median age | 39.9 years (vs Illinois 39.1y) |
Sources: Census ACS 5-Year 2024 — county-level query · Refreshed 2026-04-28
Race, Ethnicity & Diversity
Of 253,694 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups).
| Census Demographics · Total Population | 253,694 people |
|---|---|
| White residents | 152,523 |
| Black residents | 70,726 |
| Asian residents | 4,174 |
| Census Demographics · Aian | 642 |
| Census Demographics · Nhpi | 58 |
| Census Demographics · Other Race | 5,705 |
| Census Demographics · Two Or More Races | 19,866 |
| Diversity Index | 55.4% |
| Asian population | 1.6% |
| Black population | 27.9% |
| Hispanic or Latino population | 5.1% |
Sources: Census ACS 5-Year 2024 — county-level query · Refreshed 2026-04-28
Citizenship & Origin
Where residents were born and their citizenship status (Census ACS).
| Census Citizenship · Total | 253,694 |
|---|---|
| Census Citizenship · Native | 245,364 |
| Residents born in this state | 146,539 |
| Residents born in another state | 94,833 |
| Census Citizenship · Foreign Born | 26,796 |
| Census Citizenship · Naturalized | 11,617 |
| Census Citizenship · Non Citizen | 3,992 |
| Foreign-born residents | 10.6% |
Sources: Census ACS 5-Year 2024 — county-level query · Refreshed 2026-04-28
Residential Stability & Migration
How long residents have lived here and where they came from. The surrounding county is losing 2,121 residents per year on net (IRS migration data).
| Migration · People moving in (annual) | 229,470 |
|---|---|
| Migration · People moving out (annual) | 231,591 |
| Migration · Net migration (in − out) | -2,121 |
| Migration · Year | 2022-2023 |
Sources: IRS SOI Migration 2022-2023
Disability
Census ACS measures self-reported functional limitations — vision, hearing, mobility, cognitive, self-care, or independent-living. The U.S. baseline disability rate is about 12–13%; rates trend higher with median age.
| Census Disability · Total Pop | 246,845 |
|---|---|
| With Disability | 37,511 |
| Pct With Disability | 15.2% |
Sources: Census ACS 5-Year 2024 — county-level query · Refreshed 2026-04-28
Group Quarters
Group quarters are non-household living arrangements counted by the Census — college dormitories, nursing homes, military barracks, group homes, correctional facilities, and similar institutional or shared housing. 0 residents live in group quarters.
| Census Group Quarters · Total | 4,823 |
|---|
Sources: Census ACS 5-Year 2024 — county-level query · Refreshed 2026-04-28
Other
| Census Mobility · Total | 250,989 |
|---|---|
| Census Mobility · Same House | 221,652 |
| Census Mobility · Same County | 15,889 |
| Census Mobility · Diff County Same State | 4,555 |
| Census Mobility · Diff State | 7,450 |
| Census Mobility · From Abroad | 1,443 |
| Census Mobility · Moved Total | 29,337 |
| Census Mobility · Pct Moved In Year | 11.7% |
| Pct White | 60.1% |
Sources: Census ACS 5-Year 2024 — county-level query · Refreshed 2026-04-28