How many people live in McHenry County, IL?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 316,000 people living in McHenry County, IL. That makes McHenry County the sixth-most populous county in Illinois. It is home to 2.5% of people living in the state.
316K
population of McHenry County, IL (2024)
2.5%
County share of the Illinois population (2024)
About 316,000 people lived in McHenry County, IL in 2024.
Population estimates, 2000–2024
What are McHenry County, IL’s age demographics?
About 56,100 McHenry County, IL residents are aged 65 and older in 2024. That represents 17.8% of its population. For comparison, the age group represents 17.9% of Illinois’ population and 18% in the US overall.
Another 69,800 McHenry County residents, or 22.1% of the population, were children under 18. For comparison, the age group represents 21.2% of Illinois’s population and 21.6% in the US overall.
A higher share of McHenry County, IL's population is aged 45–64 than the US as a whole.
Population estimates by age group, (2024)
What are McHenry County, IL’s racial and ethnic demographics?
Non-Hispanic white residents make up 76.1% of the McHenry County, IL population, higher than the national share of 57.5%.
In contrast, McHenry County’s non-Hispanic Black or African American population accounts for 1.9%, below the 12.6% nationwide, and the Hispanic population makes up 17% of the county, compared with 20% nationally.
Racial and ethnic make up differ based on location. These figures reflect how people identified their race alone (not in combination with other races), and separate out Hispanic or Latino ethnicity, following Census reporting standards.
McHenry County, IL has a higher share of a non-Hispanic white population than Illinois as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in McHenry County, IL is Crystal Lake with about 23,800 residents in 2024.
Cities and towns in McHenry County, IL ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Crystal Lake (pt.) | 23,828 |
| 2. | Huntley (pt.) | 22,679 |
| 3. | McHenry (pt.) | 21,260 |
| 4. | Woodstock (pt.) | 18,078 |
| 5. | Algonquin (pt.) | 18,053 |
| 6. | Cary | 18,031 |
| 7. | Lake in the Hills (pt.) | 15,886 |
| 8. | Lake in the Hills (pt.) | 12,820 |
| 9. | Crystal Lake (pt.) | 9,152 |
| 10. | Crystal Lake (pt.) | 7,955 |
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Methodology
USAFacts standardizes data, in areas such as time and demographics, to make it easier to understand and compare.
The analysis was generated with the help of AI and reviewed by USAFacts for accuracy.
Page sources
USAFacts endeavors to share the most up-to-date information available. We sourced the data on this page directly from government agencies; however, the intervals at which agencies publish updated data vary.
