County Maps US

Alexander County, Illinois

A county in Illinois, ranked 99 of 102 by population.

CountyFIPS 17003

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

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Population
4,570
-602 (-11.6%) since 2020
Land area
235.4
square miles. A further 6.8% of the total area is water
Population density
19.4
people per square mile, computed rather than published
County seat
Cairo
Seat of county government.
Established
1819
206 years ago
Largest city
Cairo city
Population 1,515.

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 Alexander 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 Alexander 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 687 by 800 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 Alexander 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
Population4,57099th of 1022,849th of 3,144
Land area235.4 sq mi97th of 1022,937th of 3,144
Population density19.4 per sq mi92nd of 1022,266th of 3,144
Median household income$47,043101st of 1022,895th of 3,143

Full data for Alexander County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population4,570Vintage 2025 Population Estimates
Population in 20205,172Vintage 2025 Population Estimates
2020 estimates base?5,239Vintage 2025 Population Estimates
Land area235.4 sq mi2025 Gazetteer Files
Water area17.2 sq mi2025 Gazetteer Files
Total area252.6 sq mi2025 Gazetteer Files
Population density?19.4 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$47,043American Community Survey 2020-2024 5-Year Estimates
Median home value$59,800American Community Survey 2020-2024 5-Year Estimates
Median age48.0American Community Survey 2020-2024 5-Year Estimates
Households1,904American Community Survey 2020-2024 5-Year Estimates
Housing units2,938American 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
-44
30 births, 74 deaths
Net migration
+2
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 Alexander 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
Pulaski CountyIllinois37 mi4,820
Mississippi CountyMissouri25 mi12,003
Scott CountyMissouri22 mi37,975
Union CountyIllinois13 mi16,656
Ballard CountyKentucky7.2 mi7,594
Cape Girardeau CountyMissouri6.9 mi83,999

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.