Neighborhood Description Crystal Lake is a city located in southeastern McHenry County in northeastern Illinois. It is named after Crystal Lake, a 230 acre (93 ha) lake 1.6 miles (2.6 km) west-southwest of downtown. The population was 38,000 at the 2000 census. Crystal Lake is the biggest city in McHenry county. Neighborhood Links Neighborhood Council Community Center Chamber of Commerce History of Other Resources in Hospitals Post Office Schools Grocery Stores Cool Places to Eat