Horseshoe Lake in Madison County

Horseshoe Lake, a National Natural Landmark, is located in the American Bottom of Illinois within the greater St. Louis metropolitan area, is 2,400 acres in size, and is the second-largest natural lake in Illinois after Lake Michigan. An oxbow lake which is a remnant of a Mississippi River meander, the lake's elevation is 403 feet above sea level. The lake is the site of Horseshoe Lake State Park, which is 2,960 acres in size. The lake is bordered by the towns of Madison and Granite City. The lake is located within Nameoki Township, about four miles east of St. Louis, Missouri.

The lake is very shallow, about three feet deep throughout most of the lake, but there is one deep spot, about 54.5 feet deep, due to dredging for sand in years past. The lake is annually drained in part to provide habitat for shorebirds.