The Mammoth Hot Springs Historic District is a 158-acre (64 ha) historic district in Yellowstone National Park comprising the administrative center for the park. It is composed of two major parts: Fort Yellowstone, the military administrative center between 1886 and 1918, and now a National Historic Landmark, and a concessions district which provides food, shopping, services, and lodging for park visitors and employees. It was added to the National Register of Historic Places on March 20, 2002, for its significance in architecture, conservation, entertainment/recreation, and military. The district includes 189 contributing buildings.