Crystal Lake is a city located in southeastern McHenry County in northeastern Illinois. It is named after Crystal Lake, a lake 1.6 miles (2.6 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 2008 the population is at 41,797. Crystal Lake is the biggest city in McHenry County.