County Maps US

McHenry County, Illinois

A county in Illinois, ranked 6 of 102 by population.

CountyFIPS 17111

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

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Population
317,751
+7,774 (+2.5%) since 2020
Land area
603.4
square miles. A further 1.3% of the total area is water
Population density
527
people per square mile, computed rather than published
County seat
Woodstock
Seat of county government.
Established
1836
189 years ago
Largest city
Crystal Lake city
Population 42,288.

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 McHenry 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 McHenry 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 736 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 McHenry 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
Population317,7516th of 102234th of 3,144
Land area603.4 sq mi34th of 1021,616th of 3,144
Population density527 per sq mi7th of 102270th of 3,144
Median household income$104,8025th of 102124th of 3,143

Full data for McHenry County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population317,751Vintage 2025 Population Estimates
Population in 2020309,977Vintage 2025 Population Estimates
2020 estimates base?310,305Vintage 2025 Population Estimates
Land area603.4 sq mi2025 Gazetteer Files
Water area7.7 sq mi2025 Gazetteer Files
Total area611.1 sq mi2025 Gazetteer Files
Population density?527 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$104,802American Community Survey 2020-2024 5-Year Estimates
Median home value$308,100American Community Survey 2020-2024 5-Year Estimates
Median age40.7American Community Survey 2020-2024 5-Year Estimates
Households117,594American Community Survey 2020-2024 5-Year Estimates
Housing units121,329American 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
+406
2,984 births, 2,578 deaths
Net migration
+1,611
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 7 areas bordering McHenry 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
Lake CountyIllinois24 mi719,339
Boone CountyIllinois23 mi53,568
Walworth CountyWisconsin21 mi106,127
Kane CountyIllinois18 mi525,757
DeKalb CountyIllinois6.0 mi101,835
Kenosha CountyWisconsin5.4 mi168,448
Cook CountyIllinois2.0 mi5,194,625

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.