The National Natural Landmarks in Colorado include 15 of the almost 600 National Natural Landmarks (NNLs) in the United States; fourteen fully within Colorado and one shared with 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 13 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, the West Bijou Site, was made in 2016. 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. (Full list...)