St. Clair County, Illinois Population 2026

Updated April 2026 · US Census ACS 2023 5-Year Estimates · 9th-largest in Illinois

The population of St. Clair County, Illinois is 254,777 as of the 2023 American Community Survey, making it the 9th-largest county in Illinois. The median household income is $70,178, the median home value is $168,800, and the median age is 39.5.

The population of St. Clair County has declined 7.1% since 2010 (270,368 → 251,149), a -0.53% annualized rate.

St. Clair County within Illinois · Source: US Census TIGER/Line via us-atlas

254,777

Population

-0.53%

Annual growth

387

People / sq mi

$70,178

Median Income

$168,800

Median Home Value

St. Clair County covers 658 sq mi of land at 387.3 people per square mile.

About St. Clair County, IL

St. Clair County is a county in Illinois with a population of 254,777. It ranks #9 among counties in Illinois by population. The median age is 39.5, in line with the national median. The population is 48.5% male and 51.5% female.

The median household income in St. Clair County is $70,178, below the US median of $74,580. 9.5% of residents live below the federal poverty level. Home values sit at a median of $168,800, with monthly rent averaging $1,032. The homeownership rate of 67.8% is higher than the national rate of 64.8%.

Educational attainment in St. Clair County reflects 30.7% of adults 25 and older holding a bachelor's degree or higher, below the national average of 34.3%. Roughly 10.9% of workers primarily work from home, below the national work-from-home rate of 14.2%. The average commute is 24.7 minutes each way.

St. Clair County Population History (2010-2024)

The county of St. Clair County had a population of 270,368 in 2010 and 251,149 in 2024, a -7.1% growth over 14 years. The peak was 270,368 in 2010. Average annual growth rate: -0.52%.

251,149

Population (2024)

270,368

Population (2010)

270,368

Peak (2010)

-0.52%

Avg Annual Growth

Year	Population	Change	Annual %	Source
2010	270,368	-	-	estimate
2011	270,097	-271	-0.10%	estimate
2012	268,748	-1,349	-0.50%	estimate
2013	266,934	-1,814	-0.67%	estimate
2014	266,061	-873	-0.33%	estimate
2015	265,008	-1,053	-0.40%	estimate
2016	263,482	-1,526	-0.58%	estimate
2017	262,881	-601	-0.23%	estimate
2018	261,631	-1,250	-0.48%	estimate
2019	259,889	-1,742	-0.67%	estimate
2020	257,070	-2,819	-1.08%	estimate
2021	255,210	-1,860	-0.72%	estimate
2022	252,947	-2,263	-0.89%	estimate
2023	252,094	-853	-0.34%	estimate
2024	251,149	-945	-0.37%	estimate

Race & Ethnicity

White	61.2%
Black or African American	28.0%
Asian	0.0%
Hispanic or Latino (any race)	2.3%
Two or More Races	0.0%

Age & Sex

39.5

Median Age

51.5%

Female

48.5%

Male

16.7%

Age 65+

Age Distribution

Under 5

5.8%

5–9

6.3%

10–14

7.1%

15–19

6.5%

20–24

5.8%

25–34

12.8%

35–44

13.2%

45–54

12.1%

55–59

6.7%

60–64

7.1%

65–74

10.3%

75–84

4.4%

85+

2.0%

Children (under 15): 19.2% · Seniors (65+): 16.7%

Income & Poverty

Median household income	$70,178$-11,524 vs state
Mean household income	$92,847
Per-capita income	$37,824
Poverty rate	9.5%+1.3% vs state
Unemployment rate	3.5%
Employment-to-population	57.9%

Top Industries by Employment

Professional & business services

23.1%

Finance & real estate

12.0%

Education & health care

10.2%

Manufacturing

8.9%

Retail trade

8.2%

Public administration

7.0%

Information

6.4%

Construction

5.2%

The largest employment sector in St. Clair County is professional & business services, accounting for 23.1% of workers.

How residents commute

1.9%

Drive alone

1.5%

Carpool

76.9%

Public transit

10.9%

Work from home

24.7 min

Avg commute

Housing

$168,800$-81,700 vs state

Median home value

$1,032

Median rent

67.8%

Homeownership rate

115,348

Total housing units

87.8%

Occupied

12.2%

Vacant

32.2%

Renter-occupied

Social & access

94.6%

With health insurance

93.3%

With broadband internet

37.6%

Foreign-born

11.8%

Veterans (18+)

15.1%

With a disability

94.7%

Speak language other than English at home

Education

92.7%

High School+

30.7%

Bachelor's+

Largest cities in Illinois

Chicago (2,707,648)Aurora (179,867)Joliet (149,785)Naperville (149,424)Rockford (147,649)Elgin (114,106)Springfield (113,714)Peoria (112,126)Waukegan (88,919)Champaign (88,822)All Illinois cities →

Other counties in Illinois

Cook County (5,185,812)DuPage County (927,263)Lake County (711,885)Will County (698,450)Kane County (516,097)McHenry County (311,366)Winnebago County (283,289)Madison County (264,631)Champaign County (206,098)Sangamon County (195,217)All Illinois counties →

Part of Illinois

Illinois demographic profile All Illinois data →

Metro areas in Illinois

Chicago (9,359,555)St. Louis (2,809,414)Davenport (381,864)Peoria (365,773)Rockford (336,605)Champaign (236,196)Springfield (207,386)Bloomington (170,882)All US metros →

County rankings

US Counties by Population Richest US Counties by Median Household Income Expensive US Counties by Home Value Educated US Counties Counties With Highest Poverty Rates Youngest US Counties by Median Age Oldest US Counties by Median Age Cheapest US Counties by Median Home Value Racially Diverse US Counties Counties With Largest Hispanic Population All rankings →

Frequently Asked Questions

St. Clair County, Illinois has a population of 254,777 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 9th-largest county in Illinois. Population density is 387 people per square mile.

The population of St. Clair County has declined 7.1% since 2010 (270,368 → 251,149), a -0.53% annualized rate.

The median household income in St. Clair County, Illinois is $70,178, with mean (average) household income of $92,847 and per-capita income of $37,824. 9.5% of residents live below the federal poverty level.

In St. Clair County, the largest racial and ethnic groups are White (61.2%), Black or African American (28.0%), Hispanic or Latino (2.3%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.

The median age in St. Clair County, Illinois is 39.5 years. Residents are 51.5% female and 48.5% male.

The median home value in St. Clair County is $168,800 and median monthly rent is $1,032. 67.8% of occupied housing units are owner-occupied. The county has 115,348 total housing units, 12.2% of which are vacant.

The largest employment sector in St. Clair County, Illinois is professional, scientific, and management services, employing 23.1% of workers. The unemployment rate is 3.5%.

Chicago is among the largest cities associated with St. Clair County, Illinois, with a population of 2,707,648.