Lake Forest is a city located in Lake County, Illinois, United States. Per the 2020 census, the population was 19,367. The city is along the shore of Lake Michigan, and is a 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.