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
Housing cost is the defining feature of Marion County: the median home is valued at $100,100. Marion County is a county in Illinois with a population of 37,294. It ranks #36 among counties in Illinois by population.
The typical household here earns about $60,839, below the US median of $78,538. Poverty runs at 11.0%, below the national 12.4%. Housing costs are among the lowest of comparable places: a median home value of $100,100, with typical rent around $771.
Fewer adults hold degrees here than in most comparable places — 17.3%, below the national 35.0%. Just 5.1% of workers are home-based, below the national 14.0%, and the average commute runs about 20 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+
Largest cities in Illinois
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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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Statewide data for Illinois
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.