McHenry County area

Population and density of McHenry County

The Census Bureau estimates that 317,751 people lived in McHenry County on July 1, 2025. That ranks #235 of 3,222 county equivalents nationally and #6 of 102 in Illinois. Since the April 1, 2020 estimates base of 310,305, the population has grown by 7,446 (+2.4%), compared with −0.8% for Illinois as a whole.

With 603.4 square miles of land, that is 527 people per square mile (203 per km²), placing McHenry County #325 nationally for density and #7 in Illinois. The median county equivalent has 47 people per square mile; the Illinois median is 44. Put another way, there are about 1.2 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in McHenry County

31 incorporated places lie at least partly in McHenry County. Together they are home to 255,589 people (80.4%); the other 62,162 (19.6%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Crystal Lake city, with 42,288 residents in the county. The county seat, Woodstock city, has 25,740 residents. By land, Barrington Hills village is the largest at 27 mi² across all its counties. Among places with at least 1,000 residents in 2020, Wonder Lake village grew fastest since then (+39.4%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside McHenry County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

McHenry County is a central county of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area, in the Chicago-Naperville-Schaumburg, IL metropolitan division. Its 13 county equivalents have 9,434,123 residents on 6,923.3 square miles of land; McHenry County accounts for 8.7% of the land and 3.4% of the residents. By combined land it ranks #27 of 393 metropolitan areas, and #3 by population. It belongs to the Chicago-Naperville, IL-IN-WI Combined Statistical Area.

ZIP codes

24 ZIP Code Tabulation Areas have land in McHenry County; 18 of them have most of their land inside the county, and the others mainly cover neighboring areas.

600106001260013600146002060021600336003460042600506005160071600726008160097600986010260135601406014260152601566018061038

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering McHenry County

McHenry County shares a land border with 7 county equivalents, including 2 in Wisconsin. It has more land than 5 of them. The largest neighbor is Cook County (944.9 mi²) and the smallest is Kenosha County (271.8 mi²). Together with its neighbors, McHenry County forms a block of 4,250.7 mi² of land, of which it holds 14.2%.

How big is McHenry County compared with U.S. states?

McHenry County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.7 times as much. Illinois’s county land could hold about 92 areas the size of McHenry County.

Another way to picture it: the same land area would fill a square about 24.6 miles (39.5 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about McHenry County?

McHenry County has more land than 1,606 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places McHenry County at #1,707 nationally by total area, 91 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 1.3%, compared with a national county-equivalent median of 1.2%. The two percentages are within 0.1 percentage points of each other. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside McHenry County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.