Crystal Lake is a city located in southeastern McHenry County in northeastern Illinois, in the Chicago suburbs. It is named after Crystal Lake, a lake located 1.6 miles (2.6 sq/km) west-southwest of downtown. Crystal Lake is also a suburb of the city of Chicago. The population was 38,000 at the 2000 census, but as of 2009 the population is at 42,142. Crystal Lake is the largest city in McHenry County. Crystal Lake is a part of the Chicago metropolitan area.