County Maps US

Rock Island County, Illinois

A county in Illinois, ranked 15 of 102 by population.

CountyFIPS 17161

Within Illinois
Rock Island County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks Rock Island, the county seat, located via the 2025 Census Gazetteer.

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Population
141,869
-2,488 (-1.7%) since 2020
Land area
427.5
square miles. A further 5.3% of the total area is water
Population density
332
people per square mile, computed rather than published
County seat
Rock Island
Seat of county government.
Established
1831
194 years ago
Largest city
Moline city
Population 42,362.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Rock Island County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Rock Island County, Illinois from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 800 by 563 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Rock Island County ranks

Position among the 102 counties of Illinois, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn IllinoisNationally
Population141,86915th of 102478th of 3,144
Land area427.5 sq mi67th of 1022,376th of 3,144
Population density332 per sq mi11th of 102400th of 3,144
Median household income$67,15950th of 1021,419th of 3,143

Full data for Rock Island County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population141,869Vintage 2025 Population Estimates
Population in 2020144,357Vintage 2025 Population Estimates
2020 estimates base?144,669Vintage 2025 Population Estimates
Land area427.5 sq mi2025 Gazetteer Files
Water area23.8 sq mi2025 Gazetteer Files
Total area451.3 sq mi2025 Gazetteer Files
Population density?332 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$67,159American Community Survey 2020-2024 5-Year Estimates
Median home value$150,400American Community Survey 2020-2024 5-Year Estimates
Median age40.3American Community Survey 2020-2024 5-Year Estimates
Households61,733American Community Survey 2020-2024 5-Year Estimates
Housing units66,759American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
+176
1,881 births, 1,705 deaths
Net migration
+94
More people moved in than moved out.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 7 areas bordering Rock Island County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Scott CountyIowa37 mi175,259
Mercer CountyIllinois33 mi15,229
Henry CountyIllinois27 mi48,095
Whiteside CountyIllinois22 mi54,121
Muscatine CountyIowa21 mi41,853
Clinton CountyIowa5.6 mi46,002
Louisa CountyIowa89 ft10,416

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

All 102 counties of Illinois

Open the interactive Illinois county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.