McHenry County, Illinois Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 6th-largest in Illinois
The population of McHenry County, Illinois is 311,366 as of the 2023 American Community Survey, making it the 6th-largest county in Illinois. The median household income is $102,836, the median home value is $286,900, and the median age is 40.4.
The population of McHenry County has grown 2.2% since 2010 (309,121 → 315,959), a +0.16% annualized rate.
311,366
Population
+0.16%
Annual growth
516
People / sq mi
$102,836
Median Income
$286,900
Median Home Value
McHenry County covers 603 sq mi of land at 516.0 people per square mile.
About McHenry County, IL
Among US counties, McHenry County stands out first on household income: a median of $102,836, above the US median of $78,538. McHenry County is a county in Illinois with a population of 311,366. That makes it one of the ten largest counties in Illinois in the country, at #6 by population.
Income is a real outlier — the median household pulls in $102,836, putting McHenry County near the top of US counties. Very few residents live in poverty — 4.1%, below the national 12.4%. Home values run above average at $286,900, with typical rent around $1,358.
Educational attainment is on the higher side for US counties — 35.2% of adults hold a four-year degree, near the national 35.0%. An unusually large 14.7% of workers are remote, close to the national 14.0%, and the average commute runs about 31 minutes each way.
Taken together, the income and housing figures place McHenry County firmly in the higher-cost, higher-earning tier of US counties — a profile that tends to track dense job markets and competitive housing.
McHenry County Population History (2010-2024)
The county of McHenry County had a population of 309,121 in 2010 and 315,959 in 2024, a 2.2% growth over 14 years. The peak was 315,959 in 2024. Average annual growth rate: 0.16%.
315,959
Population (2024)
309,121
Population (2010)
315,959
Peak (2024)
0.16%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 309,121 |
| 2011 | 308,519 |
| 2012 | 308,248 |
| 2013 | 307,629 |
| 2014 | 307,425 |
| 2015 | 307,595 |
| 2016 | 307,142 |
| 2017 | 307,842 |
| 2018 | 308,145 |
| 2019 | 307,439 |
| 2020 | 309,973 |
| 2021 | 311,669 |
| 2022 | 311,921 |
| 2023 | 313,435 |
| 2024 | 315,959 |
Race & Ethnicity
| White | 82.4% |
| Black or African American | 1.6% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 1.2% |
| Two or More Races | 0.0% |
Age & Sex
40.4
Median Age
49.9%
Female
50.1%
Male
15.9%
Age 65+
Age Distribution
Children (under 15): 18.5% · Seniors (65+): 15.9%
Income & Poverty
| Median household income | $102,836+$21,134 vs state |
| Mean household income | $128,231 |
| Per-capita income | $48,275 |
| Poverty rate | 4.1%-4.1% vs state |
| Unemployment rate | 3.3% |
| Employment-to-population | 66.6% |
Top Industries by Employment
The largest employment sector in McHenry County is professional & business services, accounting for 20.2% of workers.
How residents commute
1.4%
Drive alone
1.0%
Carpool
74.9%
Public transit
14.7%
Work from home
30.6 min
Avg commute
Housing
$286,900+$36,400 vs state
Median home value
$1,358
Median rent
82.6%
Homeownership rate
120,605
Total housing units
96.5%
Occupied
3.5%
Vacant
17.4%
Renter-occupied
Social & access
95.3%
With health insurance
97.2%
With broadband internet
16.4%
Foreign-born
5.5%
Veterans (18+)
9.9%
With a disability
84.6%
Speak language other than English at home
Education
93.7%
High School+
35.2%
Bachelor's+
Largest cities in Illinois
Other counties in Illinois
Part of Illinois
Metro areas in Illinois
County rankings
Frequently Asked Questions
McHenry County, Illinois has a population of 311,366 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 6th-largest county in Illinois. Population density is 516 people per square mile.
The population of McHenry County has grown 2.2% since 2010 (309,121 → 315,959), a +0.16% annualized rate.
The median household income in McHenry County, Illinois is $102,836, with mean (average) household income of $128,231 and per-capita income of $48,275. 4.1% of residents live below the federal poverty level.
In McHenry County, the largest racial and ethnic groups are White (82.4%), Black or African American (1.6%), Hispanic or Latino (1.2%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in McHenry County, Illinois is 40.4 years. Residents are 49.9% female and 50.1% male.
The median home value in McHenry County is $286,900 and median monthly rent is $1,358. 82.6% of occupied housing units are owner-occupied. The county has 120,605 total housing units, 3.5% of which are vacant.
The largest employment sector in McHenry County, Illinois is professional, scientific, and management services, employing 20.2% of workers. The unemployment rate is 3.3%.
Chicago is among the largest cities associated with McHenry County, Illinois, with a population of 2,707,648.
McHenry County, IL Climate
McHenry County, IL has an average annual temperature of 8.5°C (47°F) and receives about 923 mm of precipitation per year. The warmest month is July and the coldest is January. Figures are 1970–2000 climate normals.
8.5°C
Avg Temp
923
Precip (mm/yr)
Jul
Hottest Month
Jan
Coldest Month
| Month | Avg (°C/°F) | Precip |
|---|---|---|
| January | -7° / 19° | 38 mm |
| February | -4° / 24° | 32 mm |
| March | 2° / 35° | 64 mm |
| April | 8° / 47° | 93 mm |
| May | 15° / 58° | 92 mm |
| June | 20° / 68° | 107 mm |
| July | 22° / 72° | 104 mm |
| August | 21° / 70° | 107 mm |
| September | 17° / 62° | 99 mm |
| October | 10° / 51° | 66 mm |
| November | 3° / 37° | 69 mm |
| December | -4° / 25° | 52 mm |
1970–2000 normals from WorldClim 2.1 (~9 km grid). Precipitation can be less precise near mountains or coastlines, where rainfall varies sharply over short distances.
Best time to visit McHenry County, IL
The most comfortable months to visit McHenry County, IL are typically August, June and July, when temperatures are mildest and rainfall is relatively low. The hottest month is July (around 29°C high). The coldest is January (near -12°C low). June is usually the wettest month.
Where to stay near McHenry County
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Data from the American Community Survey (ACS) 5-Year estimates.
Source: U.S. Census Bureau ACS, 2026.