The National Natural Landmarks (NNLs) in Illinois include 18 of the almost 600 such landmarks in the United States. They cover areas of geological, biological and historical importance, and include lakes, bogs, canyons and forests. Several of the sites provide habitat for rare or endangered plant and animal species. The landmarks are located in 13 of the state's 102 counties. Five counties each contain all or part of two or more NNLs, while one landmark is split between two counties. The first designation, Forest of the Wabash, was made in 1965, while the most recent designation, Markham Prairie, was made in 1987. Natural Landmarks in Illinois range from 53 to 6,500 acres (21.4 to 2,630.5 ha; 0.1 to 10.2 sq mi) in size.