McHenry County, Illinois

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McHenry County
County
Old McHenry County Courthouse in Woodstock, Illinois
Flag Seal
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 42°19′N 88°27′W / 42.32°N 88.45°W / 42.32; -88.45
Country	United States
State	Illinois
Founded	January 16, 1836 [1]
Named for	William McHenry
Seat	Woodstock
Largest city	Crystal Lake
Area
• Total	611 sq mi (1,580 km2)
• Land	603 sq mi (1,560 km2)
• Water	7.6 sq mi (20 km2)  1.3%
Population  (2020)
• Total	310,229
• Estimate  (2023)	312,800
• Density	510/sq mi (200/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional districts	9th, 10th, 11th, 16th
Website	www.mchenrycountyil.gov

McHenry County is a county located in the U.S. state of Illinois. According to the 2020 Census, it had a population of 310,229,^[2] making it the sixth-most populous county in Illinois. Its county seat is Woodstock.^[3] McHenry County is one of the five Illinois collar counties in the Chicago-Naperville-Elgin, IL-IN-WI Metropolitan Statistical 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.