There are 16 National Natural Landmarks in Colorado, one of which extends into Wyoming. They cover areas of geological, biological and historical importance, and include lakes, mountains, rock formations and numerous fossil sites. The landmarks are located in 14 of the state's 64 counties. Four counties each contain all or part of two NNLs, while two landmarks are split between two counties. The first two designations, Slumgullion Earthflow and Summit Lake, were made in 1965, while the most recent designation, Sulphur Cave and Spring, was made in 2021.[1][2][3] Natural Landmarks in Colorado range from 60 to 380,000 acres (24.3 to 153,780.5ha; 0.1 to 593.8sqmi) in size. Owners include private individuals and several municipal, state and federal agencies.[4]
The National Natural Landmarks Program is administered by the National Park Service, a branch of the Department of the Interior. The National Park Service determines which properties meet NNL criteria and, after notifying the owners, makes nomination recommendations. The Secretary of the Interior reviews nominations and, based on a set of predetermined criteria, makes a decision on NNL designation or a determination of eligibility for designation. Both public and privately owned properties can be designated as NNLs. Owners may object to the nomination of the property as a NNL.[5] This designation provides indirect, partial protection of the historic integrity of the properties via tax incentives, grants, monitoring of threats, and other means.[6]
The site showcases the lithologic character of sedimentary rocks, as well as providing a habitat for North American honey ants and excellent viewing opportunities for several bird species.[8]
Located in Pike National Forest, with extensive rock formations, including gorges, ridges and spires, and stream channels that meander between above- and under-ground.
Site of major paleontological importance, unique for fossil footprints of reptiles, birds, and mammals. The site was expanded in 2011 to include the 19-acre (7.69ha; 0.03sqmi)Parfet Prehistoric Preserve in the city of Golden.[12]
Protected by a thick lava cap, Raton Mesa has resisted the extensive erosion and weathering that has affected surrounding areas, providing an extreme contrast in geography.
Site showcases typical Colorado Front Range sedimentary strata, as well as erosion of Fountain Formationsandstone in unusual patterns, extensive fossil remains and unusual plant populations.
Colorado's largest remaining bulrush marsh, now rare in the southern Rocky Mountains. Provides habitat for extensive flora and fauna, especially waterfowl.
Shared with Wyoming, the site is one of North America's most impressive occurrences of cross-beddedsandstone and "topple blocks". Also a site of paleontological and biological significance.
A major example of the geologic process of mass wasting, a large flow of volcanic rock traveled from mountainside to valley to form Lake San Cristobal. The same process is occurring again, slowly covering the existing flow. Located on Bureau of Land Management land.
Located in San Isabel National Forest, the site is an exceptional illustration of over 500 igneousdikes, many exposed, formed when molten igneous rock is forced into a fault before hardening.
At almost 13,000 feet (4,000m), the site contains an excellent example of alpine tundra in the contiguous US. Some of the plants that survive in this microclimate are usually found only in the Arctic Circle.
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.
There are more than 1,500 properties and historic districts in the U.S. State of Colorado listed on the National Register of Historic Places. They are distributed over 63 of Colorado's 64 counties; only the City and County of Broomfield currently has none.
Slumgullion Pass is a mountain pass in southwestern Colorado traversed by State Highway 149 east of Lake City. The north side has the steepest grade of any continuously paved road in Colorado (9%), but the pass does not close often in winter because snowplows clear the route regularly during this season. It has a few switchbacks and tight spots, but other than that, most travelers will find it an easy, scenic route.
The Slumgullion Earthflow is a remnant of a landslide in the San Juan Mountains in Hinsdale County, Colorado. It was designated a National Natural Landmark in 1983. It is also a Colorado Natural Area and an Area of Critical Environmental Concern.
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