The Mammoth Hot Springs Historic District in Yellowstone National Park comprises the administrative center for the park. It is composed of two major parts: Fort Yellowstone, the military administrative center between 1886-1918, and now a National Historic Landmark, and a concessions district which provides food, shopping, services, and lodging for park visitors and employees.
Fort Yellowstone is a carefully ordered district of substantial buildings that clearly indicate their military origins. The U.S. Army administered the park from 1886 to 1918 when administration was transferred to National Park Service. The park headquarters is now housed in the original double cavalry barracks (constructed in 1909). The Horace Albright Visitor Center is located in the old bachelors' officers quarters (constructed in 1909).
The concessions district contrasts with the military district, with a less formal arrangement and style and includes the Mammoth Hot Springs Hotel and Dining Room, a gas station, and retail stores. The Yellowstone Main Post Office, itself on the National Register of Historic Places sits just north of Fort Yellowstone. The residential area includes houses designed by architect Robert Reamer.