McHenry County, Illinois population
County or county equivalent · Official geographic code 17111
· Annual resident population estimate
U.S. Census Bureau · Population Estimates Program · Vintage 2025
+2,021 residents (+0.64%) since July 1, 2024.
McHenry County had an estimated 317,751 residents on July 1, 2025, the 6th most populous of 102 counties and county equivalents in Illinois. Its population grew 0.64% between July 2024 and July 2025, compared with +0.13% for Illinois and +0.52% for the United States.
- Population change, 2020–2025
- +7,774July 1 to July 1 · +2.51%
- Land-area density, 2025
- 526.6People per square mile · 2025 land area
- Rank in Illinois, 2025
- 6 of 102234 of 3,144 nationally
McHenry County population history
Open historical explorerThe six July 1 estimates in the table belong to one consistent Vintage 2025 series. The Census Bureau revises earlier years when it releases a new vintage; a figure from an older publication may differ from the value below.
Vintage 2025, July 1, 2020–2025 Intercensal, 2010–2020
The highest observed population in this annual series was 317,751 in 2025. This is a peak within 2020–2025 coverage, not an all-time record.
| Reference date | Population | Annual change |
|---|---|---|
| July 1, 2020 | 309,977 | — |
| July 1, 2021 | 311,702 | +1,725 |
| July 1, 2022 | 311,889 | +187 |
| July 1, 2023 | 313,421 | +1,532 |
| July 1, 2024 | 315,730 | +2,309 |
| July 1, 2025 | 317,751 | +2,021 |
Why is the April 2020 estimates base different from a census count?
The PEP estimates base here is 310,305 residents on April 1, 2020. It incorporates the Census Bureau’s corrections and geographic revisions and serves as the starting point for this annual series. It is not labeled an original 2020 census count. The chart starts at July 1, 2020, so its five-year change uses two July observations. Read about measurement types.
McHenry County population by year, 2010–2020
From the April 2010 estimates base to the April 2020 census count, McHenry County gained 1,331 residents (+0.4%). These Census Bureau intercensal estimates use 2020 boundaries and were released in November 2024.
| Date | Population | Annual change |
|---|---|---|
| April 1, 2010 · estimates base | 308,886 | — |
| July 1, 2010 | 309,216 | — |
| July 1, 2011 | 308,997 | -219 |
| July 1, 2012 | 309,109 | +112 |
| July 1, 2013 | 308,873 | -236 |
| July 1, 2014 | 309,052 | +179 |
| July 1, 2015 | 309,604 | +552 |
| July 1, 2016 | 309,534 | -70 |
| July 1, 2017 | 310,617 | +1,083 |
| July 1, 2018 | 311,302 | +685 |
| July 1, 2019 | 310,979 | -323 |
| April 1, 2020 · census count | 310,217 | — |
The April 2020 census count (310,217) and the Vintage 2025 April 2020 base (310,305) differ by 88. The gap comes from boundary changes and the Census Bureau’s revised 2020 base, not population change, so measure growth within one series. Source and download
Growth and density
Between July 1, 2020 and July 1, 2025, McHenry County gained 7,774 residents, a 2.51% increase. The annualized change over these five elapsed years was +0.50%. Annualized change is a summary of the interval; it does not imply that the population changed at that rate in every year.
The 2025 Gazetteer reports 603.40 square miles of land. Dividing the July 1, 2025 population by that compatible land area gives 526.6 people per square mile. Water area is excluded. Density depends on geographic boundaries. It describes this entire geography, rather than a typical neighborhood or built-up area.
Calculations use unrounded source values. Population counts are displayed as integers, percentages to two decimals and density to one decimal. Calculation methods · Growth calculator
Components of population change
The published components cover July 1, 2024 through June 30, 2025. Natural change equals births minus deaths. Net migration is arrivals minus departures; it does not establish why people moved.
| Component | People |
|---|---|
| Births | 2,984 |
| Deaths | 2,578 |
| Natural change | +406 |
| Net domestic migration | +1,494 |
| Net international migration | +117 |
| Residual | +4 |
| Total population change | +2,021 |
Reconciliation: natural change + net domestic migration + net international migration + residual = +2,021. Births and deaths are already included in natural change and must not be added again. Source: co-est2025-alldata.csv; Vintage 2025.
How McHenry County compares
Growth rates below use the same Vintage 2025 series for every row, so they can be compared directly. A county’s rate reflects all of its towns and unincorporated areas together.
| Geography | Population · 2025 | Growth · 2024–25 | Growth · 2020–25 |
|---|---|---|---|
| McHenry County | 317,751 | +0.64% | +2.51% |
| Illinois | 12,719,141 | +0.13% | -0.60% |
| United States | 341,784,857 | +0.52% | +3.08% |
McHenry County demographics: age, race and income
The median age in McHenry County is 40.7 years, compared with 39.0 in Illinois. 35.2% of adults 25 and older hold a bachelor’s degree or higher, and the median household income is $104,802. About 6.2% of residents live below the poverty level, and 9.9% were born outside the United States.
These are American Community Survey 5-year estimates for 2020–2024. They describe the 60 months ending in December 2024, come from a sample survey with the margins of error shown, and are separate from the July 1, 2025 population estimate above.
| Characteristic | McHenry County | Margin | Illinois | U.S. |
|---|---|---|---|---|
| Age and sex | ||||
| Median age | 40.7 | ±0.3 | 39.0 | 38.9 |
| Under 18 years | 22.7% | ±0.4 | 21.8% | 22.0% |
| 65 years and over | 16.5% | ±0.5 | 17.0% | 17.2% |
| Female | 49.9% | ±0.1 | 50.6% | 50.5% |
| Race and Hispanic origin | ||||
| Hispanic or Latino (any race) | 16.1% | ±<0.1 | 18.8% | 19.3% |
| White alone, not Hispanic | 76.1% | ±0.3 | 58.1% | 57.4% |
| Black alone, not Hispanic | 1.4% | ±0.1 | 13.3% | 11.9% |
| Asian alone, not Hispanic | 3.0% | ±0.1 | 5.9% | 5.9% |
| American Indian and Alaska Native, not Hispanic | 0.0% | ±<0.1 | 0.1% | 0.5% |
| Native Hawaiian and Pacific Islander, not Hispanic | 0.0% | ±<0.1 | 0.0% | 0.2% |
| Some other race, not Hispanic | 0.2% * | ±0.1 | 0.4% | 0.6% |
| Two or more races, not Hispanic | 3.2% | ±0.3 | 3.4% | 4.3% |
| Born outside the United States | 9.9% | ±0.5 | 14.7% | 14.1% |
| Households and education | ||||
| Households | 117,594 | ±563 | 5,036,449 | 129,227,496 |
| Average household size | 2.64 | ±0.01 | 2.46 | 2.53 |
| Bachelor’s degree or higher, age 25+ | 35.2% | ±1.0 | 37.8% | 35.7% |
| Income and poverty | ||||
| Median household income | $104,802 | ±$2,178 | $83,390 | $80,734 |
| Below the poverty level | 6.2% | ±0.6 | 11.8% | 12.5% |
Margins are 90% margins of error. * The margin is large relative to the estimate (coefficient of variation above 30%); treat it as approximate. Percentages are computed from published Summary File counts with Census Bureau margin formulas. ACS survey population: 312,591; 2024 boundaries. Source and download
Geographic context
County equivalents include parishes, boroughs, census areas, independent cities, DC and Connecticut planning regions where represented by Census. The places listed below are whole-city observations and can extend into other counties. Summing them will not reproduce this county total.
| Place | Population · 2025 | Change · 2024–25 | Growth · 2024–25 | People / sq. mi. |
|---|---|---|---|---|
| Crystal LakeIllinois · Incorporated place · 1717887 | 42,288 | +789 | +1.90% | 2,229.7 |
| AlgonquinIllinois · Incorporated place · 1700685 | 30,824 | +296 | +0.97% | 2,445.2 |
| McHenryIllinois · Incorporated place · 1745694 | 29,217 | +381 | +1.32% | 1,942.9 |
| HuntleyIllinois · Incorporated place · 1736750 | 29,132 | +655 | +2.30% | 1,988.2 |
| Lake in the HillsIllinois · Incorporated place · 1741183 | 28,590 | -97 | -0.34% | 2,793.7 |
| WoodstockIllinois · Incorporated place · 1783349 | 25,740 | -132 | -0.51% | 1,947.1 |
| CaryIllinois · Incorporated place · 1711592 | 17,932 | -73 | -0.41% | 2,747.9 |
| Fox LakeIllinois · Incorporated place · 1727442 | 10,849 | -29 | -0.27% | 1,385.0 |
| HarvardIllinois · Incorporated place · 1733331 | 9,504 | +93 | +0.99% | 1,134.5 |
| HampshireIllinois · Incorporated place · 1732525 | 9,266 | +374 | +4.21% | 918.6 |
Showing 10 of 31 related records.
Illinois population · State city directory · City proper versus county versus metro
Illinois counties and county equivalents with nearby population ranks
Neighboring 2025 population ranks within Illinois. Similar population does not imply similar density, boundaries or demographics.
| Place | Population · 2025 | Change · 2024–25 | Growth · 2024–25 | People / sq. mi. |
|---|---|---|---|---|
| Will County | 712,253 | +3,273 | +0.46% | 852.1 |
| Kane County | 525,757 | +2,327 | +0.44% | 1,012.3 |
| Winnebago County | 283,674 | +709 | +0.25% | 552.9 |
| Madison County | 263,110 | -207 | -0.08% | 367.7 |
Source, citation and downloads
U.S. Census Bureau, Population Estimates Program, Vintage 2025, co-est2025-alldata.csv, variable POPESTIMATE2025; McHenry County, Illinois, geographic code 17111; resident population 317,751 on July 1, 2025; boundaries January 1, 2025. https://www2.census.gov/programs-surveys/popest/datasets/2020-2025/counties/totals/co-est2025-alldata.csv. Retrieved September 30, 2026. US Population Data snapshot pep-2025-r1, transformation 1.
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