Rock Island County, Illinois Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 14th-largest in Illinois
The population of Rock Island County, Illinois is 142,995 as of the 2023 American Community Survey, making it the 14th-largest county in Illinois. The median household income is $66,768, the median home value is $144,700, and the median age is 40.3.
The population of Rock Island County has declined 3.3% since 2010 (147,613 → 142,731), a -0.24% annualized rate.
142,995
Population
-0.24%
Annual growth
334
People / sq mi
$66,768
Median Income
$144,700
Median Home Value
Rock Island County covers 427 sq mi of land at 334.5 people per square mile.
About Rock Island County, IL
What distinguishes Rock Island County is density: among the most densely settled of US counties, around 334 people per square mile. With 142,995 residents, Rock Island County is a county in Illinois. It ranks #14 among counties in Illinois by population.
Median household income is $66,768, below the US median of $78,538. Poverty runs at 11.1%, below the national 12.4%. Homes carry a median value of $144,700, with typical rent around $863.
Degree attainment is mid-range for US counties: 24.1% of adults hold a four-year degree, below the national 35.0%. About 6.7% of the workforce is home-based, below the national 14.0%, and the average commute runs about 20 minutes each way.
That density explains much of the rest of the profile in Rock Island County: denser places lean toward renting, shorter commutes by transit, and a younger working-age mix.
Rock Island County Population History (2010-2024)
The county of Rock Island County had a population of 147,613 in 2010 and 142,731 in 2024, a -3.3% growth over 14 years. The peak was 147,699 in 2012. Average annual growth rate: -0.24%.
142,731
Population (2024)
147,613
Population (2010)
147,699
Peak (2012)
-0.24%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 147,613 |
| 2011 | 147,474 |
| 2012 | 147,699 |
| 2013 | 147,686 |
| 2014 | 147,090 |
| 2015 | 146,161 |
| 2016 | 144,977 |
| 2017 | 143,824 |
| 2018 | 142,522 |
| 2019 | 141,775 |
| 2020 | 144,360 |
| 2021 | 142,943 |
| 2022 | 141,812 |
| 2023 | 141,939 |
| 2024 | 142,731 |
Race & Ethnicity
| White | 73.0% |
| Black or African American | 11.0% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 1.4% |
| Two or More Races | 0.2% |
Age & Sex
40.3
Median Age
50.5%
Female
49.5%
Male
20.1%
Age 65+
Age Distribution
Children (under 15): 18.7% · Seniors (65+): 20.1%
Income & Poverty
| Median household income | $66,768$-14,934 vs state |
| Mean household income | $83,668 |
| Per-capita income | $35,753 |
| Poverty rate | 11.1%+2.9% vs state |
| Unemployment rate | 3.5% |
| Employment-to-population | 57.7% |
Top Industries by Employment
The largest employment sector in Rock Island County is professional & business services, accounting for 22.5% of workers.
How residents commute
1.5%
Drive alone
3.2%
Carpool
79.1%
Public transit
6.7%
Work from home
20.2 min
Avg commute
Housing
$144,700$-105,800 vs state
Median home value
$863
Median rent
68.6%
Homeownership rate
66,742
Total housing units
91.7%
Occupied
8.3%
Vacant
31.4%
Renter-occupied
Social & access
94.0%
With health insurance
93.7%
With broadband internet
26.4%
Foreign-born
7.2%
Veterans (18+)
15.1%
With a disability
86.5%
Speak language other than English at home
Education
90.2%
High School+
24.1%
Bachelor's+
Largest cities in Illinois
Other counties in Illinois
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County rankings
Frequently Asked Questions
Rock Island County, Illinois has a population of 142,995 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 14th-largest county in Illinois. Population density is 334 people per square mile.
The population of Rock Island County has declined 3.3% since 2010 (147,613 → 142,731), a -0.24% annualized rate.
The median household income in Rock Island County, Illinois is $66,768, with mean (average) household income of $83,668 and per-capita income of $35,753. 11.1% of residents live below the federal poverty level.
In Rock Island County, the largest racial and ethnic groups are White (73.0%), Black or African American (11.0%), Hispanic or Latino (1.4%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in Rock Island County, Illinois is 40.3 years. Residents are 50.5% female and 49.5% male.
The median home value in Rock Island County is $144,700 and median monthly rent is $863. 68.6% of occupied housing units are owner-occupied. The county has 66,742 total housing units, 8.3% of which are vacant.
The largest employment sector in Rock Island County, Illinois is professional, scientific, and management services, employing 22.5% of workers. The unemployment rate is 3.5%.
Chicago is among the largest cities associated with Rock Island County, Illinois, with a population of 2,707,648.
Rock Island County, IL Climate
Rock Island County, IL has an average annual temperature of 10.1°C (50°F) and receives about 930 mm of precipitation per year. The warmest month is July and the coldest is January. Figures are 1970–2000 climate normals.
10.1°C
Avg Temp
930
Precip (mm/yr)
Jul
Hottest Month
Jan
Coldest Month
| Month | Avg (°C/°F) | Precip |
|---|---|---|
| January | -6° / 21° | 37 mm |
| February | -3° / 27° | 29 mm |
| March | 4° / 38° | 66 mm |
| April | 10° / 51° | 94 mm |
| May | 17° / 62° | 99 mm |
| June | 22° / 71° | 108 mm |
| July | 24° / 76° | 118 mm |
| August | 23° / 73° | 102 mm |
| September | 18° / 65° | 97 mm |
| October | 12° / 53° | 69 mm |
| November | 4° / 39° | 61 mm |
| December | -3° / 27° | 50 mm |
1970–2000 normals from WorldClim 2.1 (~9 km grid). Precipitation can be less precise near mountains or coastlines, where rainfall varies sharply over short distances.
Best time to visit Rock Island County, IL
The most comfortable months to visit Rock Island County, IL are typically June, August and September, when temperatures are mildest and rainfall is relatively low. The hottest month is July (around 30°C high). The coldest is January (near -11°C low). July is usually the wettest month.
Where to stay near Rock Island County
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Data from the American Community Survey (ACS) 5-Year estimates.
Source: U.S. Census Bureau ACS, 2026.