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St. Clair County, Illinois Demographics 2026

St. Clair County, Illinois has a population of 253,694, the 9th most populous county in Illinois. The median household income is $73,854 and the median home value is $180,300. The poverty rate is 13.6%.

Data vintage: U.S. Census Bureau ACS 2020–2024 5-Year Estimates · refreshed July 2026 · Methodology & source notes

St. Clair County Quick Facts

Population 253,694
Median Household Income $73,854
Median Home Value $180,300
Poverty Rate 13.6%
Unemployment Rate 6.0%
Median Age 39.9 years
Homeownership Rate 68.4%
Affordability Ratio 2.4x
Bachelor's Degree+ 31.8%
High School Graduation 93.5%
Cities/Places 29
Population 253,694 9th of 102
Median Income $73,854 11% lower than state
Poverty Rate 13.6%
Unemployment 6.0%

How St. Clair County Changed

Change from the 2019–2023 ACS period to 2020–2024. These are rolling five-year estimates, not year-over-year measurements.

Metric2019–20232020–2024Change
Population254,777253,694-0.4%
Median household income$70,178$73,854+5.2%
Median home value$168,800$180,300+6.8%

Economy & Housing

Household Income Distribution

Under $25K 16.8%
$25K-$50K 18.4%
$50K-$100K 28.7%
$100K+ 36.0%
Detailed income brackets
Under $10K
5.8%
$10K-$15K
3.7%
$15K-$20K
2.9%
$20K-$25K
4.4%
$25K-$30K
3.4%
$30K-$35K
3.6%
$35K-$40K
3.6%
$40K-$45K
4.0%
$45K-$50K
3.8%
$50K-$60K
6.3%
$60K-$75K
9.1%
$75K-$100K
13.3%
$100K-$125K
10.0%
$125K-$150K
7.0%
$150K-$200K
9.4%
$200K+
9.6%

Employment

6.0% Unemployment Rate State: 5.8%|National: 5.2%
63.3% Labor Force Participation

Housing Overview

Owner 68.4%
Renter 31.6%
Affordability Index Very Affordable
2.4x home value to income ratio
Median gross rent $1,090/mo 17.7% of median household income annually

People & Demographics

Diversity Index

57out of 100
High Diversity

A diverse community with significant representation from multiple racial and ethnic groups.

State average: 61 | National average: 61

Education

Cities & Places in St. Clair County

CityPopulationMedian IncomePovertyHome Value
Belleville41,370$63,53514.6%$141,300
O'Fallon32,262$105,9826.2%$295,700
East St. Louis17,999$35,70032.8%$52,600
Fairview Heights16,745$80,9308.8%$177,700
Swansea14,710$91,5878.7%$223,600
Shiloh14,572$99,5736.8%$274,000
Columbia11,127$107,6065.4%$293,000
Mascoutah8,816$97,3759.8%$224,900
Freeburg4,592$92,0656.7%$241,200
Lebanon4,474$88,75014.8%$170,700
Caseyville4,130$60,66914.3%$96,800
Millstadt4,008$90,9017.4%$230,500
Scott AFB3,957$103,3905.7%N/A
Dupo3,879$61,6448.5%$113,800
Smithton3,680$135,4553.4%$256,300
New Baden3,463$81,3937.4%$172,200
New Athens1,933$56,55311.5%$116,300
Washington Park1,701$38,75035.2%$37,500
Marissa1,232$54,81412.8%$99,500
Brooklyn729$30,67344.3%$37,500
St. Libory559$116,9645.2%$178,800
Hecker521$79,5832.4%$166,800
Lenzburg428$42,65621.6%$77,900
Fayetteville357$59,58315.2%$95,200
Sauget307$62,1718.5%$51,400
Summerfield248$51,94414.9%$75,700
East Carondelet233$67,50011.2%$58,600
Paderborn20N/A0.0%N/A
Darmstadt18N/A0.0%N/A

Explore Illinois Rankings

Cities by Population All cities ranked by size Richest Cities Ranked by median income Most Educated By bachelor's degree rate Most Affordable By housing affordability

Population Overview

St. Clair County is located in Illinois with a total population of 253,694. It is the 9th most populous county out of 102 in Illinois. The county encompasses 29 Census-designated places.

Age Demographics

The median age in St. Clair County is 39.9 years. This is 2% higher than the state median of 39.0 years.

Economy, Income & Housing

The median household income in St. Clair County is $73,854. This is 11% lower than the state median of $83,390. It is also 9% lower than the national median of $80,734. The poverty rate stands at 13.6%. This is 15% higher than the state poverty rate of 11.8%. The unemployment rate is 6.0%. This is 2% higher than the state rate of 5.8%. The median home value is $180,300. Housing costs are 32% lower than the state median of $263,300. With a home-value-to-income ratio of just 2.4x, St. Clair County is one of the most affordable housing markets in the area. 68.4% of occupied housing units are owner-occupied. This homeownership rate is 2% higher than the state average of 67.1%.

Race & Ethnicity

The largest racial or ethnic group in St. Clair County is White (non-Hispanic), making up 59.1% of the population. Black or African American residents account for 27.7%. The Black or African American population is significantly higher than the state average (27.7% vs 13.3%). The Hispanic or Latino population (5.1%) is well below the state average of 18.8%. The Asian population (1.6%) is well below the state average of 5.9%.

Education

31.8% of residents aged 25 and older hold a bachelor's degree or higher. This is 16% lower than the state rate of 37.9%. Nationally, 35.7% of adults hold at least a bachelor's degree. The high school graduation rate (or equivalent) is 93.5%.

Data Sources & Methodology

All figures for St. Clair County come from the U.S. Census Bureau's American Community Survey (ACS) 2020–2024 5-Year Estimates, with comparisons drawn against Illinois and national averages from the same dataset. See our methodology page for how each metric is defined, or data.census.gov for official tables with margins of error.

Frequently Asked Questions

What is the population of St. Clair County, Illinois?

St. Clair County has a population of 253,694, making it the 9th most populous county in Illinois.

What is the median income in St. Clair County?

The median household income in St. Clair County is $73,854 with a poverty rate of 13.6%.

How many cities are in St. Clair County, Illinois?

St. Clair County contains 29 Census-designated places.