Williamson County, Illinois Population 2026

Updated April 2026 · US Census ACS 2023 5-Year Estimates · 22nd-largest in Illinois

The population of Williamson County, Illinois is 66,902 as of the 2023 American Community Survey, making it the 22nd-largest county in Illinois. The median household income is $65,521, the median home value is $145,600, and the median age is 41.4.

The population of Williamson County has grown 0.9% since 2010 (66,440 → 67,064), a +0.07% annualized rate.

Williamson County within Illinois · Source: US Census TIGER/Line via us-atlas

66,902

Population

+0.07%

Annual growth

159

People / sq mi

$65,521

Median Income

$145,600

Median Home Value

Williamson County covers 420 sq mi of land at 159.2 people per square mile.

About Williamson County, IL

Williamson County is a county in Illinois with a population of 66,902. It ranks #22 among counties in Illinois by population. The median age is 41.4, older than the national median. The population is 50.3% male and 49.7% female.

The median household income in Williamson County is $65,521, below the US median of $74,580. 10.1% of residents live below the federal poverty level. Home values sit at a median of $145,600, with monthly rent averaging $897. The homeownership rate of 71.1% is higher than the national rate of 64.8%.

Educational attainment in Williamson County reflects 27.5% of adults 25 and older holding a bachelor's degree or higher, below the national average of 34.3%. Roughly 8.6% of workers primarily work from home, below the national work-from-home rate of 14.2%. The average commute is 23.2 minutes each way.

Williamson County Population History (2010-2024)

The county of Williamson County had a population of 66,440 in 2010 and 67,064 in 2024, a 0.9% growth over 14 years. The peak was 67,504 in 2016. Average annual growth rate: 0.07%.

67,064

Population (2024)

66,440

Population (2010)

67,504

Peak (2016)

0.07%

Avg Annual Growth

Year	Population	Change	Annual %	Source
2010	66,440	-	-	estimate
2011	66,745	+305	+0.46%	estimate
2012	66,793	+48	+0.07%	estimate
2013	67,472	+679	+1.02%	estimate
2014	67,439	-33	-0.05%	estimate
2015	67,457	+18	+0.03%	estimate
2016	67,504	+47	+0.07%	estimate
2017	67,076	-428	-0.63%	estimate
2018	67,017	-59	-0.09%	estimate
2019	66,633	-384	-0.57%	estimate
2020	67,121	+488	+0.73%	estimate
2021	66,895	-226	-0.34%	estimate
2022	66,565	-330	-0.49%	estimate
2023	66,737	+172	+0.26%	estimate
2024	67,064	+327	+0.49%	estimate

Race & Ethnicity

White	89.2%
Black or African American	3.5%
Asian	0.1%
Hispanic or Latino (any race)	2.1%
Two or More Races	0.0%

Age & Sex

41.4

Median Age

49.7%

Female

50.3%

Male

19.6%

Age 65+

Age Distribution

Under 5

5.4%

5–9

5.9%

10–14

6.5%

15–19

5.4%

20–24

4.9%

25–34

12.7%

35–44

13.5%

45–54

12.4%

55–59

6.5%

60–64

7.1%

65–74

11.5%

75–84

6.2%

85+

1.9%

Children (under 15): 17.8% · Seniors (65+): 19.6%

Income & Poverty

Median household income	$65,521$-16,181 vs state
Mean household income	$85,557
Per-capita income	$37,096
Poverty rate	10.1%+1.9% vs state
Unemployment rate	2.5%
Employment-to-population	55.5%

Top Industries by Employment

Professional & business services

30.8%

Manufacturing

8.3%

Information

8.3%

Education & health care

7.4%

Finance & real estate

6.0%

Retail trade

5.4%

Construction

5.4%

Public administration

5.4%

The largest employment sector in Williamson County is professional & business services, accounting for 30.8% of workers.

How residents commute

0.3%

Drive alone

0.8%

Carpool

81.5%

Public transit

8.6%

Work from home

23.2 min

Avg commute

Housing

$145,600$-104,900 vs state

Median home value

$897

Median rent

71.1%

Homeownership rate

31,957

Total housing units

90.0%

Occupied

10.0%

Vacant

28.9%

Renter-occupied

Social & access

94.8%

With health insurance

92.1%

With broadband internet

21.1%

Foreign-born

8.7%

Veterans (18+)

19.0%

With a disability

96.5%

Speak language other than English at home

Education

92.4%

High School+

27.5%

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)St. Clair County (254,777)Champaign County (206,098)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

Williamson County, Illinois has a population of 66,902 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 22nd-largest county in Illinois. Population density is 159 people per square mile.

The population of Williamson County has grown 0.9% since 2010 (66,440 → 67,064), a +0.07% annualized rate.

The median household income in Williamson County, Illinois is $65,521, with mean (average) household income of $85,557 and per-capita income of $37,096. 10.1% of residents live below the federal poverty level.

In Williamson County, the largest racial and ethnic groups are White (89.2%), Black or African American (3.5%), Hispanic or Latino (2.1%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.

The median age in Williamson County, Illinois is 41.4 years. Residents are 49.7% female and 50.3% male.

The median home value in Williamson County is $145,600 and median monthly rent is $897. 71.1% of occupied housing units are owner-occupied. The county has 31,957 total housing units, 10.0% of which are vacant.

The largest employment sector in Williamson County, Illinois is professional, scientific, and management services, employing 30.8% of workers. The unemployment rate is 2.5%.

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