County Maps US

Carroll County, Illinois

A county in Illinois, ranked 67 of 102 by population.

CountyFIPS 17015

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

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Population
15,419
-267 (-1.7%) since 2020
Land area
445.4
square miles. A further 4.6% of the total area is water
Population density
34.6
people per square mile, computed rather than published
County seat
Mount Carroll
Seat of county government.
Established
1839
186 years ago
Largest city
Savanna city
Population 2,699.

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 Carroll 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 Carroll 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 497 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 Carroll 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
Population15,41967th of 1022,068th of 3,144
Land area445.4 sq mi60th of 1022,285th of 3,144
Population density34.6 per sq mi68th of 1021,801st of 3,144
Median household income$60,75880th of 1022,013th of 3,143

Full data for Carroll County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population15,419Vintage 2025 Population Estimates
Population in 202015,686Vintage 2025 Population Estimates
2020 estimates base?15,720Vintage 2025 Population Estimates
Land area445.4 sq mi2025 Gazetteer Files
Water area21.6 sq mi2025 Gazetteer Files
Total area467 sq mi2025 Gazetteer Files
Population density?34.6 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$60,758American Community Survey 2020-2024 5-Year Estimates
Median home value$114,500American Community Survey 2020-2024 5-Year Estimates
Median age45.4American Community Survey 2020-2024 5-Year Estimates
Households6,578American Community Survey 2020-2024 5-Year Estimates
Housing units8,204American 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
-72
137 births, 209 deaths
Net migration
+24
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 6 areas bordering Carroll 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
Whiteside CountyIllinois24 mi54,121
Jo Daviess CountyIllinois20 mi21,594
Ogle CountyIllinois19 mi51,399
Jackson CountyIowa16 mi19,288
Stephenson CountyIllinois12 mi43,220
Clinton CountyIowa7.9 mi46,002

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.