County Maps US

Adams County, Illinois

A county in Illinois, ranked 23 of 102 by population.

CountyFIPS 17001

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

Download SVGFull Illinois map downloads

Population
64,267
-1,370 (-2.1%) since 2020
Land area
855.2
square miles. A further 1.9% of the total area is water
Population density
75.2
people per square mile, computed rather than published
County seat
Quincy
Seat of county government.
Established
1825
200 years ago
Largest city
Quincy city
Population 38,918.

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 Adams 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 Adams 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 773 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 Adams 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
Population64,26723rd of 102851st of 3,144
Land area855.2 sq mi12th of 102975th of 3,144
Population density75.2 per sq mi32nd of 1021,130th of 3,144
Median household income$66,22055th of 1021,506th of 3,143

Full data for Adams County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population64,267Vintage 2025 Population Estimates
Population in 202065,637Vintage 2025 Population Estimates
2020 estimates base?65,745Vintage 2025 Population Estimates
Land area855.2 sq mi2025 Gazetteer Files
Water area16.1 sq mi2025 Gazetteer Files
Total area871.3 sq mi2025 Gazetteer Files
Population density?75.2 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$66,220American Community Survey 2020-2024 5-Year Estimates
Median home value$162,600American Community Survey 2020-2024 5-Year Estimates
Median age41.4American Community Survey 2020-2024 5-Year Estimates
Households27,915American Community Survey 2020-2024 5-Year Estimates
Housing units30,302American 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
-67
694 births, 761 deaths
Net migration
+116
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 Adams 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
Hancock CountyIllinois31 mi16,803
Pike CountyIllinois30 mi14,231
Lewis CountyMissouri19 mi9,879
Brown CountyIllinois18 mi6,401
Marion CountyMissouri16 mi28,525
Schuyler CountyIllinois6.1 mi6,657

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.