Crystal Lake is a city located in southeastern McHenry County in northeastern Illinois. It is named after Crystal Lake, a 230 acre lake.6 miles west-southwest of downtown. The population was 38,000 at the 2000 census. Crystal Lake is the biggest city in McHenry county, and is the economic and cultural center of the far northwestern suburbs of Chicago, despite not being the county's governmental center. Crystal Lake apartments for rent comparison page shows most up to date rent information on Crystal Lake apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.