National Natural Landmark

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 July 2024, 605 sites have been added to the National Registry of Natural Landmarks. The registry includes nationally significant geological and ecological features in 48 states, American Samoa, Guam, Puerto Rico, and the U.S. Virgin Islands.

The National Park Service administers the NNL Program and, if requested, assists NNL owners and managers with the conservation of these sites. Land acquisition by the federal government is not a goal of the 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, the designation of a National Natural Landmark constitutes only an agreement with the owner to preserve, as far 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.

Designation

The NNL designation is made by the Secretary of the Interior after an in-depth scientific study of a potential site. All new designations must have owner concurrence. The selection process is rigorous: to be considered for NNL status, a site must be one of the best examples of a natural region's characteristic biotic or geologic features. Since the establishment of the NNL program, a multi-step process has been used to designate a site for NNL status. Since 1970, the following steps have constituted the process.

1. A natural area inventory of a natural region is completed to identify the most promising sites.
2. After landowners are notified that the site is being considered for NNL status, a detailed onsite evaluation is conducted by scientists other than those who conducted the inventory.
3. The evaluation report is peer-reviewed by other experts to assure its soundness.
4. The report is reviewed further by National Park Service staff.
5. The site is reviewed by the Secretary of the Interior's National Park Advisory Board to determine that the site qualifies as an NNL.
6. The findings are provided to the Secretary of the Interior who approves or declines.
7. Landowners are notified a third time informing them that the site has been designated an NNL.

Prospective sites for NNL designation are terrestrial and aquatic ecosystems; geological features, exposures, and landforms that record active geological processes or portions of earth history; and fossil evidence of biological evolution. Each major natural history "theme" can be further subdivided into various sub-themes. For example, sub-themes suggested in 1972 for the overall theme "Lakes and ponds" included large deep lakes, large shallow lakes, lakes of complex shape, crater lakes, kettle lake and potholes, oxbow lakes, dune lakes, sphagnum-bog lakes, lakes fed by thermal streams, tundra lakes and ponds, swamps and marshy areas, sinkhole lakes, unusually productive lakes, and lakes of high productivity and high clarity.