Horseshoe Lake State Park is an Illinois state park in Madison County, Illinois, United States. It is approximately 2960 acre and surrounds a large horseshoe-shaped lake called Horseshoe Lake. Horseshoe Lake is the second largest natural lake in Illinois taking up approximately 2400 acre of the 2960 acre park. The park has connections to Madison County Transit's Schoolhouse Trail, which connects to over 85 mi of bike trail in Madison County, and even a trail which goes all of the way to downtown St. Louis after crossing the Mississippi River on the Chain of Rocks Bridge. The park is located in southeastern Granite City, Illinois, 10 mi northeast of downtown St. Louis.