| McHenry County Illinois Cities/Towns - Algonquin, Bull Valley, Cary, Crystal Lake, Greenwood, Harvard, Hebron, Holiday Hills, Island Lake, Johnsburg, Lake In The Hills, Lakewood, Marengo, McCullom Lake, McHenry, Oakwood Hills, Pistakee Highlands, Prairie Grove, Richmond, Spring Grove, Trout Valley, Union, Wonder Lake, Woodstock (County Seat) |
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Your Ad Here McHenry County is located in the U.S. state of Illinois. As of 2008, the U.S. Census Bureau estimated the population to be 318,641. Its county seat is Woodstock. History McHenry County was formed in 1836. The county was named for Major William McHenry, an Indian fighter who died in Vandalia in 1835.  |