Lake Forest is a city in Lake County, Illinois, United States. The population was 19,367 at the 2020 census. The city is along the shore of Lake Michigan, and is part of the Chicago metropolitan area and the North Shore. Lake Forest was founded with Lake Forest College and was laid out as a town in 1857, a stop for travelers making their way south to Chicago. The Lake Forest City Hall, designed by Charles Sumner Frost, was completed in 1898. It originally housed the fire department, the Lake Forest Library, and city offices.