The City of Lake St. Louis is a planned community, and suburb of greater St. Louis, situated around two lakes between Interstate 70 and Interst…The City of Lake St. Louis is a planned community, and suburb of greater St. Louis, situated around two lakes between Interstate 70 and Interstate 64 in western St. Charles County, Missouri, United States. The population was 16,707 as of the 2020 US Census. Lake St. Louis, is 43 miles from the city of St. Louis.