Formed January 16, 1836 (64th county)
McHenry County (310,227), Woodstock (25,634), Crystal Lake (40,259)
A Modern style red and tan brick courthouse built in 1972 and expanded in 1990 to serve this county. It is sited in the northern part of the city on Seminary Avenue at Russell Street. Illinois State Highway 47 is Seminary Avenue. Johnson, Kile, Seehausen, and Associates are the architects. There were 1857 and 1972 versions of the courthouse in Woodstock. McHenry was the first county seat until 1843 when Woodstock assumed the role. McHenry County was created on January 16, 1836 from Cook and La Salle counties as the 64th county. The county is named for cavalryman Major William McHenry. Woodstock is named for Woodstock, Vermont.
McHenry County government consists of a sheriff, an attorney, a coroner, a clerk, a treasurer, and an assessor (executive). It has 19 Board Members (legislative.) Nineteen Circuit Court Judges and a court clerk serve McHenry County (judicial.) The county is on the northern border with Wisconsin. Chicago, Illinois is southeast and Rockford, Illinois is west of the county. The county center is 5.9 miles East of Woodstock in Bull Valley. The county is surrounded clockwise by Wisconsin and Lake, Cook, Kane, De Kalb, and Boone counties.
The area of the county is 603 square miles. It is 34 out of 102 in the state. It ranks 6 out of 102 in population in the state. It has a density of 514.5 persons per square mile making it 7 out of 102 in the state. McHenry County has 79.7% of its population in its incorporated areas. Interstate Highway 90 cuts the southwest corner of the county from Kane County, southeast, to Boone County, west. United States Highway 12 cuts the northeast corner from Wisconsin, north, to Lake County, east. United States Highway 14 goes north to southeast through the county from Wisconsin to Lake County. United States Highway 20 parallels Interstate Highway 90 from Kane to Boone counties. The county is rectangular. Woodstock is near the center of the county. Crystal Lake is in the southeast quarter of the county. Woodstock is the county seat and Crystal Lake is the largest city. Woodstock is 8.3% of the county population while Crystal Lake is 13.0% of the county population. This county is in the Chicago-Naperville-Joliet Metropolitan Statistical Area.
Bull Valley
Cary
Crystal Lake
Greenwood
Harvard
Hebron
Holiday Hills
Johnsburg
Lake in the Hills
Lakewood
Marengo
McCullom Lake
McHenry
Oakwood Hills
Prairie Grove
Richmond
Ringwood
Spring Grove
Trout Valley
Union
Wonder Lake
Woodstock
Algonquin
Barrington Hills
Fox Lake
Fox River Grove
Huntley
Island Lake
Lakemoor
Port Barrington