Mercer County, Illinois Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 69th-largest in Illinois
The population of Mercer County, Illinois is 15,619 as of the 2023 American Community Survey, making it the 69th-largest county in Illinois. The median household income is $71,710, the median home value is $139,300, and the median age is 44.5.
The population of Mercer County has declined 6.8% since 2010 (16,410 → 15,292), a -0.50% annualized rate.
15,619
Population
-0.50%
Annual growth
28
People / sq mi
$71,710
Median Income
$139,300
Median Home Value
Mercer County covers 561 sq mi of land at 27.8 people per square mile.
About Mercer County, IL
Mercer County is a county in Illinois with a population of 15,619. It ranks #69 among counties in Illinois by population. The median age is 44.5, older than the national median. The population is 50.5% male and 49.5% female.
The median household income in Mercer County is $71,710, near the US median of $74,580. 5.6% of residents live below the federal poverty level. Home values sit at a median of $139,300, with monthly rent averaging $757. The homeownership rate of 82.7% is higher than the national rate of 64.8%.
Educational attainment in Mercer County reflects 18.9% of adults 25 and older holding a bachelor's degree or higher, below the national average of 34.3%. Roughly 7.8% of workers primarily work from home, below the national work-from-home rate of 14.2%. The average commute is 28.5 minutes each way.
Mercer County Population History (2010-2024)
The county of Mercer County had a population of 16,410 in 2010 and 15,292 in 2024, a -6.8% growth over 14 years. The peak was 16,410 in 2010. Average annual growth rate: -0.50%.
15,292
Population (2024)
16,410
Population (2010)
16,410
Peak (2010)
-0.50%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 16,410 |
| 2011 | 16,320 |
| 2012 | 16,165 |
| 2013 | 16,077 |
| 2014 | 15,902 |
| 2015 | 15,748 |
| 2016 | 15,611 |
| 2017 | 15,618 |
| 2018 | 15,572 |
| 2019 | 15,490 |
| 2020 | 15,632 |
| 2021 | 15,583 |
| 2022 | 15,512 |
| 2023 | 15,456 |
| 2024 | 15,292 |
Race & Ethnicity
| White | 94.8% |
| Black or African American | 0.6% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 0.6% |
| Two or More Races | 0.0% |
Age & Sex
44.5
Median Age
49.5%
Female
50.5%
Male
21.4%
Age 65+
Age Distribution
Children (under 15): 16.8% · Seniors (65+): 21.4%
Income & Poverty
| Median household income | $71,710$-9,992 vs state |
| Mean household income | $87,773 |
| Per-capita income | $36,295 |
| Poverty rate | 5.6%-2.6% vs state |
| Unemployment rate | 1.8% |
| Employment-to-population | 58.3% |
Top Industries by Employment
The largest employment sector in Mercer County is professional & business services, accounting for 20.5% of workers.
How residents commute
0.1%
Drive alone
2.2%
Carpool
81.4%
Public transit
7.8%
Work from home
28.5 min
Avg commute
Housing
$139,300$-111,200 vs state
Median home value
$757
Median rent
82.7%
Homeownership rate
7,279
Total housing units
88.1%
Occupied
11.9%
Vacant
17.3%
Renter-occupied
Social & access
94.8%
With health insurance
91.6%
With broadband internet
29.0%
Foreign-born
8.7%
Veterans (18+)
12.8%
With a disability
97.1%
Speak language other than English at home
Education
93.3%
High School+
18.9%
Bachelor's+
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County rankings
Frequently Asked Questions
Mercer County, Illinois has a population of 15,619 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 69th-largest county in Illinois. Population density is 28 people per square mile.
The population of Mercer County has declined 6.8% since 2010 (16,410 → 15,292), a -0.50% annualized rate.
The median household income in Mercer County, Illinois is $71,710, with mean (average) household income of $87,773 and per-capita income of $36,295. 5.6% of residents live below the federal poverty level.
In Mercer County, the largest racial and ethnic groups are White (94.8%), Black or African American (0.6%), Hispanic or Latino (0.6%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in Mercer County, Illinois is 44.5 years. Residents are 49.5% female and 50.5% male.
The median home value in Mercer County is $139,300 and median monthly rent is $757. 82.7% of occupied housing units are owner-occupied. The county has 7,279 total housing units, 11.9% of which are vacant.
The largest employment sector in Mercer County, Illinois is professional, scientific, and management services, employing 20.5% of workers. The unemployment rate is 1.8%.
Chicago is among the largest cities associated with Mercer 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.