County Maps US

Mason County, Illinois

A county in Illinois, ranked 82 of 102 by population.

CountyFIPS 17125

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

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Population
12,411
-639 (-4.9%) since 2020
Land area
539.4
square miles. A further 4.3% of the total area is water
Population density
23.0
people per square mile, computed rather than published
County seat
Havana
Seat of county government.
Established
1841
184 years ago
Largest city
Havana city
Population 2,799.

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 Mason 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 Mason 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 564 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 Mason 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
Population12,41182nd of 1022,259th of 3,144
Land area539.4 sq mi48th of 1021,940th of 3,144
Population density23.0 per sq mi86th of 1022,128th of 3,144
Median household income$62,84569th of 1021,817th of 3,143

Full data for Mason County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population12,411Vintage 2025 Population Estimates
Population in 202013,050Vintage 2025 Population Estimates
2020 estimates base?13,082Vintage 2025 Population Estimates
Land area539.4 sq mi2025 Gazetteer Files
Water area24.2 sq mi2025 Gazetteer Files
Total area563.6 sq mi2025 Gazetteer Files
Population density?23.0 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$62,845American Community Survey 2020-2024 5-Year Estimates
Median home value$103,400American Community Survey 2020-2024 5-Year Estimates
Median age45.4American Community Survey 2020-2024 5-Year Estimates
Households5,781American Community Survey 2020-2024 5-Year Estimates
Housing units6,622American 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
-107
108 births, 215 deaths
Net migration
+31
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 Mason 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
Menard CountyIllinois41 mi11,863
Cass CountyIllinois40 mi12,463
Tazewell CountyIllinois25 mi130,049
Fulton CountyIllinois25 mi32,901
Logan CountyIllinois14 mi27,182
Schuyler CountyIllinois11 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.