St. Clair County's 2026 population is estimated at 250,041, reflecting a -0.27% growth rate over the past year (World Population Review estimate based on U.S. Census Bureau data). St. Clair County is the 9th largest county in Illinois. The 2010 population was 270,368 and has grown -7.52% since 2010.
Overall: 39.9 years
Female: 40.9 years
Male: 38.6 years
There are 195,281 adults, (44,007 of whom are seniors) in St. Clair County.
Female: 130,583 (51.5%)
Male: 123,111 (48.5%)
The racial composition of St. Clair County includes 60.12% White, 27.88% Black or African American, and smaller percentages for other race, Asian, Native American, Native Hawaiian or Pacific Islander and multiracial populations.
| Race | Population ↓ | Percentage (of total) |
|---|---|---|
| White | 152,523 | 60.12% |
| Black or African American | 70,726 | 27.88% |
| Two or more races | 19,866 | 7.83% |
| Other race | 5,705 | 2.25% |
| Asian | 4,174 | 1.65% |
| Native American | 642 | 0.25% |
| Native Hawaiian or Pacific Islander | 58 | 0.02% |
St. Clair County 's average per capita income is $50,612. Household income levels show a median of $73,854. The poverty rate stands at 13.58%.
| Name | Median ↓ | Mean |
|---|---|---|
| Married Families | $120,148 | $140,125 |
| Families | $97,289 | $117,809 |
| Households | $73,854 | $96,049 |
| Non Families | $42,031 | $55,053 |
Average Income
Median Household Income
Poverty Rate