9th most populous of 102
With 251,149 residents in 2024, St. Clair County ranks 9th by population among Illinois's 102 counties and is home to 2.0% of the state's residents.
St. Clair County is home to 251,149 people (2024 estimate) on 658 square miles of land. This page brings together official U.S. Census Bureau population estimates since 2000, the components of change—births, deaths and migration—American Community Survey indicators on income, housing, poverty and education, BEA economic accounts and BLS unemployment.
Key indicators
Population
251,149
July 1, 2024 estimate
2020 Census base
257,631
April 1, 2020
Change since 2020
−2.5%
2020–2024
Land area
658 mi²
1,704 km²
Population density
381.8 /mi²
2024 estimate ÷ land area
Births
2,139
Year to July 1, 2024
Deaths
2,817
Year to July 1, 2024
Natural change
−678
Births minus deaths, 2024
Net migration
−268
Domestic + international, 2024
Per capita personal income
$61,712
BEA, 2024
Gross domestic product
$16.1 billion
BEA, current dollars, 2024
Median household income
$73,854
ACS 2020–2024 5-year
Poverty rate
13.6%
ACS 2020–2024 5-year
Bachelor’s degree or higher
31.8%
Age 25+, ACS 2020–2024 5-year
Foreign-born residents
3.3%
ACS 2020–2024 5-year
Median home value
$180,300
ACS 2020–2024 5-year
Unemployment rate
4.7%
BLS annual average, 2024
Historical data
Pick an indicator to see its long-run evolution.
Population
2000–2024251,149▼ 2%
U.S. Census Bureau: intercensal estimates 2000–2009, Vintage 2020 (2010–2019) and Vintage 2024 (2020–2024), July 1.
Data summary
| Indicator | Value | Year and source |
|---|---|---|
| Population estimate | 251,149 | 2024 · U.S. Census Bureau |
| Population, 2010 Census | 270,056 | 2010 · U.S. Census Bureau |
| Population, 2000 | 256,462 | July 1, 2000 · Census intercensal |
| Change since 2000 | −2.1% | 2000–2024 · Census |
| International migration | +597 | 2024 · Census Vintage 2024 |
| Domestic migration | −865 | 2024 · Census Vintage 2024 |
| Birth rate | 8.5 per 1,000 | 2024 · calculated |
| Death rate | 11.2 per 1,000 | 2024 · calculated |
| Population rank in Illinois | 9th of 102 | 2024 · calculated |
| Per capita personal income | $61,712 | BEA, 2024 · official |
| Gross domestic product | $16.1 billion | BEA, current dollars, 2024 · official |
| Median household income | $73,854 | ACS 2020–2024 5-year · official |
| Poverty rate | 13.6% | ACS 2020–2024 5-year · official |
| Bachelor’s degree or higher | 31.8% | Age 25+, ACS 2020–2024 5-year · official |
| Foreign-born residents | 3.3% | ACS 2020–2024 5-year · official |
| Median home value | $180,300 | ACS 2020–2024 5-year · official |
| Median gross rent | $1,090/month | ACS 2020–2024 5-year · official |
| Median age | 39.9 years | ACS 2020–2024 5-year · official |
| Households | 100,846 | ACS 2020–2024 5-year · official |
| Owner-occupied homes | 68.4% | ACS 2020–2024 5-year · official |
St. Clair County in context
Comparable indicators for St. Clair County, Illinois and the United States.
| Indicator | County | Illinois | U.S. | Reference |
|---|---|---|---|---|
| Population change 2020–2024 | −2.5% | −0.9% | +2.6% | Census Vintage 2024 |
| Birth rate (per 1,000) | 8.5 | 9.9 | 10.6 | 2024 |
| Death rate (per 1,000) | 11.2 | 9.0 | 9.1 | 2024 |
| Net migration rate (per 1,000) | -1.1 | 4.5 | 8.2 | 2024 |
| Population density (/mi²) | 381.8 | 229.0 | 96.3 | 2024 |
| Per capita personal income | $61,712 | $74,522 | $73,204 | BEA, 2024 |
| Median household income | $73,854 | $83,390 | $80,734 | ACS 2020–2024 5-year |
| Poverty rate | 13.6% | 11.8% | 12.5% | ACS 2020–2024 5-year |
| Bachelor’s degree or higher | 31.8% | 37.8% | 35.7% | Age 25+, ACS 2020–2024 5-year |
| Foreign-born residents | 3.3% | 14.7% | 14.1% | ACS 2020–2024 5-year |
| Median home value | $180,300 | $263,300 | $332,700 | ACS 2020–2024 5-year |
| Median gross rent | $1,090/month | $1,274/month | $1,413/month | ACS 2020–2024 5-year |
| Median age | 39.9 years | 39.0 years | 38.9 years | ACS 2020–2024 5-year |
| Owner-occupied homes | 68.4% | 67.1% | 65.2% | ACS 2020–2024 5-year |
Did you know? St. Clair County
A quarter century of change
Its population went from 256,462 in 2000 to 251,149 in 2024, a change of −2.1%, compared with +2.2% for Illinois as a whole.
Births and deaths
In the year to July 2024 the county recorded 2,139 births and 2,817 deaths, so deaths outnumbered births by 678.
Peak population in 2010
Annual Census estimates since 2000 put the county's highest population at 270,368 in 2010. The 2024 figure is 19,219 lower.
9th in density
St. Clair County has about 381.8 residents per square mile of land, ranking 9th of 102 counties; Illinois averages 229.0.
Household income rank
With a median household income of $73,854 (ACS 2020–2024 5-year), the county ranks 29th of 102 Illinois counties; the state median is $83,390.
Size of the economy
Its economy produced $16.1 billion of GDP in 2024 (BEA), 10th largest among 102 Illinois counties.
Latest economic growth
Real GDP grew 1.1% in 2024, adjusted for inflation (BEA, chained 2017 dollars).
Sources and methodology
- U.S. Census Bureau — County population totals and components, Vintage 2024
- U.S. Census Bureau — County estimates 2010–2020
- U.S. Census Bureau — Intercensal estimates 2000–2010
- U.S. Census Bureau — Gazetteer files (land area)
- U.S. Census Bureau — American Community Survey 2020–2024 5-year
- U.S. Bureau of Economic Analysis — Regional economic accounts
- U.S. Bureau of Labor Statistics — LAUS