The National Natural Landmarks (NNLs) in Wisconsin include 18 of the almost 600 such landmarks in the United States. They cover areas of geological, biological and historical importance, and include dune and swales, swamps, bogs, and virgin forests. Several of the sites provide habitat for rare or endangered plant and animal species. The Driftless Area in southwest Wisconsin is known for its rare species, especially in the Baraboo Range. Owners include private individuals, Native American tribes, and several county, state and federal agencies. These landmarks were designed between 1967 and 1987. They vary in size between 44 and 53,531 acres (18 and 21,663 hectares).