McHenry County
Also known as McHenry County, Illinois, McHenry County, IL
county in Illinois, United States
Key facts
- Country
- United States
- State
- Illinois
- Founded
- January 16, 1836
- Named after
- William McHenry
- Seat
- Woodstock
- Largest city
- Crystal Lake
- Total
- 611 sq mi (1,580 km )
- Land
- 603 sq mi (1,560 km )
- Water
- 7.6 sq mi (20 km ) 1.3%
- Estimate 2025
- 317,751
- Density
- 514/sq mi (199/km )
- Time zone
- UTC−6 ( Central )
- Summer dst
- UTC−5 ( CDT )
Article
McHenry County is located in the U.S. state of Illinois. According to the 2020 Census, it had a population of 310,229, making it the sixth-most populous county in Illinois. Its county seat is Woodstock. McHenry County is one of the five Illinois collar counties in the Chicago metropolitan area. Long known as a center of recreation along with agriculture in the western portion, it has recently experienced rapid rates of suburbanization, exurbanization and urbanization, but the western segment of the county remains primarily agricultural and rural.
History