County Maps US

Union County, Illinois

A county in Illinois, ranked 63 of 102 by population.

CountyFIPS 17181

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

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Population
16,656
-643 (-3.7%) since 2020
Land area
413.4
square miles. A further 2.1% of the total area is water
Population density
40.3
people per square mile, computed rather than published
County seat
Jonesboro
Seat of county government.
Established
1818
207 years ago
Largest city
Anna city
Population 4,096.

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 Union 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 Union 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 592 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 Union 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
Population16,65663rd of 1021,997th of 3,144
Land area413.4 sq mi71st of 1022,446th of 3,144
Population density40.3 per sq mi57th of 1021,668th of 3,144
Median household income$55,72893rd of 1022,423rd of 3,143

Full data for Union County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population16,656Vintage 2025 Population Estimates
Population in 202017,299Vintage 2025 Population Estimates
2020 estimates base?17,350Vintage 2025 Population Estimates
Land area413.4 sq mi2025 Gazetteer Files
Water area8.7 sq mi2025 Gazetteer Files
Total area422.1 sq mi2025 Gazetteer Files
Population density?40.3 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$55,728American Community Survey 2020-2024 5-Year Estimates
Median home value$131,700American Community Survey 2020-2024 5-Year Estimates
Median age44.3American Community Survey 2020-2024 5-Year Estimates
Households6,868American Community Survey 2020-2024 5-Year Estimates
Housing units7,851American 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
-118
147 births, 265 deaths
Net migration
-57
More people moved out than moved in.

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

The 7 areas bordering Union 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
Jackson CountyIllinois24 mi52,501
Cape Girardeau CountyMissouri20 mi83,999
Johnson CountyIllinois18 mi13,363
Alexander CountyIllinois13 mi4,570
Pulaski CountyIllinois11 mi4,820
Williamson CountyIllinois6.2 mi67,225
Perry CountyMissouri0.4 mi19,093

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.