Horseshoe Lake (Madison County Illinois)
 Horseshoe Lake a National Natural Landmark is located in the American Bottom of Illinois within the greater St. Louis metropolitan area is 2400 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 2960 acres (12 km2) in size.