List of National Natural Landmarks

The National Natural Landmarks (NNL) Program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only national natural areas program that identifies and recognizes the best examples of biological and geological features in both public and private ownership. The program was established on May 18, 1962, by United States Secretary of the Interior Stewart Udall.

The program aims to encourage and support voluntary preservation of sites that illustrate the geological and ecological history of the United States. It also hopes to strengthen the public's appreciation of the country's natural heritage. As of November 2016, 599 sites have been added to the National Registry of National Landmarks. The registry includes nationally significant geological and ecological features in 48 states, American Samoa, Guam, Puerto Rico, and the Virgin Islands.

The National Park Service administers the NNL Program and if requested, assists NNL owners and managers with the conservation of these important sites. Land acquisition by the federal government is not a goal of this program. National Natural Landmarks are nationally significant sites owned by a variety of land stewards, and their participation in this federal program is voluntary.

The legislative authority for the National Natural Landmarks Program stems from the Historic Sites Act of August 21, 1935 (49 Stat. 666, 16 U.S.C. 641); the program is governed by federal regulations. The NNL Program does not have the protection features of Section 106 of the National Historic Preservation Act of 1966. Thus, designation of a National Natural Landmark presently constitutes only an agreement with the owner to preserve, insofar as possible, the significant natural values of the site or area. Administration and preservation of National Natural Landmarks is solely the owner's responsibility. Either party may terminate the agreement after they notify the other.

...
Wikipedia