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 (10 km²) 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 (123 m) above sea level. The lake is the site of Horseshoe Lake State Park, which is 2,960 acres (12 km²) in size. The lake is bordered by the towns of Madison and Granite City; it is located within Nameoki Township, about four miles east of St.