Marion County, Illinois Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 36th-largest in Illinois
The population of Marion County, Illinois is 37,294 as of the 2023 American Community Survey, making it the 36th-largest county in Illinois. The median household income is $60,839, the median home value is $100,100, and the median age is 41.3.
The population of Marion County has declined 7.6% since 2010 (39,416 → 36,437), a -0.56% annualized rate.
37,294
Population
-0.56%
Annual growth
65
People / sq mi
$60,839
Median Income
$100,100
Median Home Value
Marion County covers 573 sq mi of land at 65.1 people per square mile.
About Marion County, IL
Marion County is a county in Illinois with a population of 37,294. It ranks #36 among counties in Illinois by population. The median age is 41.3, older than the national median. The population is 49.1% male and 50.9% female.
The median household income in Marion County is $60,839, below the US median of $74,580. 11.0% of residents live below the federal poverty level. Home values sit at a median of $100,100, with monthly rent averaging $771. The homeownership rate of 74.5% is higher than the national rate of 64.8%.
Educational attainment in Marion County reflects 17.3% of adults 25 and older holding a bachelor's degree or higher, below the national average of 34.3%. Roughly 5.1% of workers primarily work from home, below the national work-from-home rate of 14.2%. The average commute is 20.4 minutes each way.
Marion County Population History (2010-2024)
The county of Marion County had a population of 39,416 in 2010 and 36,437 in 2024, a -7.6% growth over 14 years. The peak was 39,416 in 2010. Average annual growth rate: -0.56%.
36,437
Population (2024)
39,416
Population (2010)
39,416
Peak (2010)
-0.56%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 39,416 |
| 2011 | 39,147 |
| 2012 | 39,018 |
| 2013 | 38,685 |
| 2014 | 38,573 |
| 2015 | 38,381 |
| 2016 | 38,057 |
| 2017 | 37,757 |
| 2018 | 37,453 |
| 2019 | 37,309 |
| 2020 | 37,657 |
| 2021 | 37,390 |
| 2022 | 36,878 |
| 2023 | 36,640 |
| 2024 | 36,437 |
Race & Ethnicity
| White | 90.4% |
| Black or African American | 4.2% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 0.5% |
| Two or More Races | 0.0% |
Age & Sex
41.3
Median Age
50.9%
Female
49.1%
Male
19.8%
Age 65+
Age Distribution
Children (under 15): 19.5% · Seniors (65+): 19.8%
Income & Poverty
| Median household income | $60,839$-20,863 vs state |
| Mean household income | $76,720 |
| Per-capita income | $32,199 |
| Poverty rate | 11.0%+2.8% vs state |
| Unemployment rate | 3.9% |
| Employment-to-population | 56.1% |
Top Industries by Employment
The largest employment sector in Marion County is professional & business services, accounting for 26.8% of workers.
How residents commute
0.2%
Drive alone
1.5%
Carpool
82.7%
Public transit
5.1%
Work from home
20.4 min
Avg commute
Housing
$100,100$-150,400 vs state
Median home value
$771
Median rent
74.5%
Homeownership rate
17,379
Total housing units
89.0%
Occupied
11.0%
Vacant
25.5%
Renter-occupied
Social & access
93.4%
With health insurance
90.2%
With broadband internet
17.9%
Foreign-born
8.4%
Veterans (18+)
18.7%
With a disability
97.7%
Speak language other than English at home
Education
90.3%
High School+
17.3%
Bachelor's+
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County rankings
Frequently Asked Questions
Marion County, Illinois has a population of 37,294 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 36th-largest county in Illinois. Population density is 65 people per square mile.
The population of Marion County has declined 7.6% since 2010 (39,416 → 36,437), a -0.56% annualized rate.
The median household income in Marion County, Illinois is $60,839, with mean (average) household income of $76,720 and per-capita income of $32,199. 11.0% of residents live below the federal poverty level.
In Marion County, the largest racial and ethnic groups are White (90.4%), Black or African American (4.2%), Hispanic or Latino (0.5%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in Marion County, Illinois is 41.3 years. Residents are 50.9% female and 49.1% male.
The median home value in Marion County is $100,100 and median monthly rent is $771. 74.5% of occupied housing units are owner-occupied. The county has 17,379 total housing units, 11.0% of which are vacant.
The largest employment sector in Marion County, Illinois is professional, scientific, and management services, employing 26.8% of workers. The unemployment rate is 3.9%.
Chicago is among the largest cities associated with Marion County, Illinois, with a population of 2,707,648.
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Population, race, income, age, and trends across Illinois
Data from the American Community Survey (ACS) 5-Year estimates.
Source: U.S. Census Bureau ACS, 2026.