Fort Yellowstone, Yellowstone National Park's historic and current administrative headquarters, lies in the northwestern part of the park, just east of the famous natural geothermal formations known as the Mammoth Hot Springs terraces. The layout of Fort Yellowstone is that of a typical western army post. A group of substantial two-and-a-half story double officers' quarters form an ''Officers' Row'' opposite an open parade ground to the west. The historic army headquarters and guard house lie at the south end of the post, facing a portion of the original road from Gardiner. Barracks for enlisted men are located in the second row of housing, while cavalry stables and noncommissioned sergeants' quarters are found behind the troop quarters. Storage and service buildings are present in the southern part of the post. The last building erected by the army at Fort Yellowstone, the chapel, is located at the extreme southern end of the administrative area. North of Officers' Row, across the wide esplanade that leads from the northern entrance road into the part headquarters, are the office and residence of the U.S. Engineer, while the jail and office of the U.S. Commissioner lies west of the parade ground. The Fort Yellowstone district encompasses the intact historic components of the army post developed during the 1886-1918 period to facilitate the protection and preservation of the area's natural features and wildlife.

Fort Yellowstone is significant under National Landmark criteria as the headquarters of the U.S. Army during its administration of Yellowstone National Park. Yellowstone was established in 1872 as the nation's first national park. Army cavalry troops were dispatched to the park in 1886, after fourteen years of underfunded and understaffed civilian administration had failed to protect its natural features and wildlife. The military established a headquarters tent camp at Mammoth Hot Springs, which evolved into Camp Sheridan (1886-1891) and Fort Yellowstone (1891-1918). While troops were used in other national parks, the army's thirty-two years in Yellowstone marked the military's longest and most extensive presence. In no other park was an official army fort established.

Fort Yellowstone is also significant under National Landmark criteria for the principles and policies toward conservation and national park stewardship developed by the army during its administration of Yellowstone National Park. In the process of carrying out day-to-day administrative tasks in the park, the military commanders promulgated rules and regulations that constituted a philosophy of conservation, that defined the nature, characteristics, and management of national parks. During the army regime in the park, wildlife was defended and even saved from extinction, and geothermal and other natural features were protected from vandalism and destruction.

The Grand Loop Road Historic District is a 140.14 mile road system which provides the primary visitor access to the major points of interest and visitor facilities in Yellowstone National Park. The current alignment of the Grand Loop Road grew from early wagon trails that followed river valleys and lakeshores. During the first 30 years of development, the road was in constant change, but by 1905 the interior road system connecting natural attractions, hotels, and entrance roads had crystallized into the present figure-eight configuration known as the Grand Loop Road. Having been built over many decades with many different standards, techniques, materials, and under many administrators, the Grand Loop Road retains basically the same configuration as it was first built, although some small sections have been abandoned or transformed into scenic roads.

The alignment is the way in which the road moves across the landscape; the curves, straight sections, and roadway movement to the left or right constitute the horizontal alignment; the movement of the roadway up and down hills being the vertical alignment. Although changes have been made to improve the road and to meet weather, natural, and geologic concerns, it is the continuation of the philosophy of design that harmonizes the road with the environment that is important. The Grand Loop Road retains elements of grace in alignment with features constructed of natural materials to a scale compatible with the natural environment, and the roadside vegetation contribute to the natural setting, evoking a feeling of distinction that differentiates it from modern roads. Landscape details such as stone curbing at pullouts, masonry culvert headwalls, guardwalls, retaining walls, and log railing were added to continue the design philosophy of using natural materials.

The Lake Hotel, prominently located on Lake Yellowstone in Yellowstone National Park, is significant as a type of construction and the work of a master. It is also important because it represents the development of concessions in Yellowstone National Park and thus played a major role in the development of tourism not only in the Park, but also in the nearby states. The building is the product of expansions to meet visitor needs. The Hotel was originally constructed in 1891. It evolved from a barracks-like structure to a large Colonial Revival edifice after its first major alteration in 1903-1904. This style is not a typical example of the hotel construction movement within the national parks at the turn of the twentieth century in which buildings were designed to harmonize with the environment as exemplified by Yellowstone's Old Faithful Inn. The concessioner's architect, Robert C. Reamer, who played a major role in the creation of a Colonial Revival style in his alterations to the hotel, is significant in the architectural history of Yellowstone National Park. In addition to his work at Lake Hotel, his other achievements in the Park are the design for the Old Faithful Inn and its additions, the Canyon Hotel, the Mammoth Dining Room, Motor Inn, and cottages, as well as the Child's residence at Mammoth Hot Springs.

Lake Hotel is the only extant hotel from this early period. The construction of the first Fishing Bridge in 1902 and the completion of the East Entrance Road which traverses the Shoshone National Forest and eventually leads to Cody, Wyoming, certainly influenced the patterns of Wyoming tourism. The opening of the road coincided with the first major addition to the hotel in 1903-1904. The decision for the construction of the hotel and its placement near one of the major natural features in the Park is a part of the history of the development of the Park's concessions. Its location also determined the planned itinerary for the early traveling public by the concessioners and offered a different experience for the guests.

The Lamar Buffalo Ranch is located just east of Rose Creek in the Lamar River Valley in the northeast quadrangle of Yellowstone National Park. The Historic District consists of five structures including a barn, two residences, a bunkhouse, and corral constructed between 1915 and the 1930s. The District is nationally significant for its role in the history of wildlife management and preservation of the bison in the United States, and for its importance in the history of park rangers in Yellowstone. Yellowstone National Park was one of the few areas that took a lead in preserving and building up the remnant herds of bison in the country. In 1902, Congress appropriated funds to save the bison from extinction. A small free-roaming bison herd was native to Yellowstone National Park and to that herd bison from semi-domesticated herds in Montana and Texas were added. Initially, the semi-domesticated herd was enclosed near Fort Yellowstone at Mammoth Hot Springs. In 1907, 28 bison from the Fort Yellowstone enclosure were moved by Army scouts to a new enclosure in the Lamar Valley (Lamar Buffalo Ranch). Park rangers have performed many of the duties at the ranch during its long period of use into the 1950s.

The Mammoth Hot Springs Historic District is significant as the administrative and concession headquarters of the largest national park in Wyoming. It is important for its historical association with the development of Yellowstone National Park and with the development of administrative and concession policies in Yellowstone and the national park system. The district's location, near one of the major natural curiosities in the park, the Mammoth Hot Springs Terraces, and at the juncture of the first entrance road to the park resulted in its selection as the site of the first administrative headquarters and the site of the first concessions in the first national park in the United States. The first hotels in Yellowstone were located at Mammoth Hot Springs, as well as the first retail store, photograph shop, and filling station, the successors of which still operate within the district. The army era in the national parks is also associated with the district, which includes Fort Yellowstone, the best-preserved post representing the early military efforts to protect the nation's natural resources. The district is also important for its association with the early history of the National Park Service, reflecting the influence of that agency on park development in areas such as preserving natural features and scenic resources, responding to the popularity of the automobile, creating museums and educational programs, and incorporating master plans in park design. The district is also associated with the history of New Deal era public works programs, having benefited from several projects which provided funding and manpower for improvements and new construction.

Mammoth Hot Springs is also significant for its architecture. Fort Yellowstone, within the district, reflects the layout and architecture of a typical western army fort of the late nineteenth century, and is remarkable for its level of integrity, the masonry displayed in its native sandstone buildings, and the substantial quality of its construction. The buildings of the military period are representative of the work of the United States Quartermaster Corps, Hiram Chittenden, and Reed and Stem. Buildings erected after the military era in the administrative area of the district are significant for their representation of the work of architects of the National Park Service, and the landscape of the district reflects the influence of the agency's master plans and the efforts of its landscape architects. Government buildings of the post-military era include fine representatives of French Renaissance and English Tudor style architecture. The concession area buildings are notable for their reflection of the evolution of park commercial architecture from the late nineteenth through the mid-twentieth centuries. Included within the district are concession buildings which are excellent representatives of Colonial Revival, Rustic, Prairie, and Art Moderne styles. The work of architects hired by concessioners, including Robert C. Reamer, Fred Wilson, and Douglas McLellan, is also represented in the district.

The three museums, designed by Herbert Maier, an American Association of Museums and Laura Spelman Rockefeller Foundation architect, are located at separate areas in Yellowstone National Park. Fishing Bridge Museum (1930-31) is on the north shore of Yellowstone Lake near the center of the Park, the Madison Museum (1929) is in the northwest quadrant of the Park, and the Norris Geyser Basin Museum (1929) is located between the two others. These museums represent nationally significant architecture for two reasons. First, the buildings are the best structures of rustic design in the National Park System. Second, because of their exaggerated architectural features and organic forms, the buildings served as models for hundreds of other buildings constructed throughout the nation in state, county, and local parks under the auspices of the National Park Service during the work relief programs of the 1930s. They have also played an important role in the history of the National Park Service by epitomizing the concept of ''trailside museums'' where visitors received orientation to the resources of an area through the Park Service's interpretive and educational programs.

The North Entrance Road Historic District is a 5.23 mile road within Yellowstone National Park. The road extends from the park boundary at Gardiner, Montana to the park headquarters at Mammoth Hot Springs. The historic district includes the road and the Roosevelt Arch near the north boundary. The road was built in the 1880s. By 1903 the Roosevelt Arch had been completed. The North Entrance Road Historic District is significant as an integral part of the planned road system in Yellowstone National Park. It is also associated with the Army Corps of Engineers role in the development of the Park. It is also a significant example of the ''blending with nature'' design philosophy first espoused by the Army Corps of Engineers and later expounded upon by the landscape architects of the National Park Service. The road alignment, its historic culverts, headwalls, and other design features continue to impart this important ''park road'' feeling to the visitor.

The Northeast Entrance Station is located at the Cooke City/Silver Gate entrance to Yellowstone National Park. It consists of two buildings: a checking station and ranger station/residence. The checking station spans most of Montana Highway 212 as it enters the Park. The ranger station/residence is a short distance away on the north side of the road. Of all of the entrance stations in national parks and monuments, the Northeast Entrance Station is a classic in terms of its classic rustic design. At the time of its construction in 1935 it was considered one of the most ambitious of its type. The buildings were designed by members of Thomas Vint's Branch of Plans and Design in San Francisco. They were constructed as a Public Works project through contract with George Larkin of Gardiner, Montana.

The Obsidian Cliff Kiosk, constructed in 1931, is significant for its outstanding representation of individuality achieved by the use of a material which is a phenomenon of the immediate environs, and because it is the first wayside exhibit built in the National Park System. The ''open air museum-in-miniature'' aids the public in understanding and enjoying the natural aspects of the nearby Obsidian Cliff, a mountain of volcanic glass which extends for approximately two miles. This exhibit was one of the many significant innovations in interpretation made by Carl Russell, which are widely reflected today in how parks are interpreted and in how they are experienced by visitors.

Obsidian Cliff, located in northwestern Yellowstone National Park, is a geologically distinctive natural feature that has been used as a raw material source for high quality obsidian tools for at least 11,000 years. The Obsidian Cliff lithic source area has been regarded as a prominent prehistoric quarry since its recognition in the 19th century. The volcanic glass was quarried and made into many types of tools, f rom simple flake tools used to cut hides or butcher animals for meat, to arrowheads or spear points, to large ceremonial artifacts. Obsidian Cliff obsidian can be found in archeological sites from the Middle Rockies into western Canada, across the Great Plains into the Midwest, as well as the Columbia Plateau, and possibly the Great Basin. By using trace-and bulk-element geochemistry techniques, archaeologists can trace obsidian artifacts to known geological sources. Obsidian from Obsidian Cliff was imported and utilized for ceremonial purposes by peoples of the Hopewell Culture in the Ohio River valley from around 1,600 to 2,200 years ago.

The Old Faithful Historic District lies on the Grand Loop Road between Madison Junction and the West Thumb area of Yellowstone National Park. The District is dominated by the Old Faithful Inn and also consists of the Old Faithful Lodge, three stores, two service stations, five dormitories, ten support buildings, and the guest cabins behind the Old Faithful Lodge and the Snow Lodge. The District is both historically and architecturally significant. The historical aspect is its role in concessions development in the early 1900s to accommodate the thousands of people who came to view the well-known symbol of the National Parks, the Old Faithful Geyser. The Old Faithful Inn, built in 1903-04, is one of the premier rustic structures in the country. The adjacent support structures, the lodge, auto camp, stores, and the gas stations which all addressed the new auto tourism, were designed to be compatible with the Inn and were constructed from circa 1916 through 1940s. The use of the rustic log architecture represents the idea of enhancing rather than detracting from the sp

irit of the wilderness. This concept, the sensitivity of the architecture to the environment, would be a model for the National Park Service for succeeding decades.

Old Faithful Inn, one of Wyoming's most innovative and spectacular historic buildings, takes its name from Old Faithful Geyser alongside which it is built in Yellowstone National Park. Designed by Robert C. Reamer, a noted Seattle Architect, construction began during the fall, winter and spring of 1903-1904, with the addition to the east wing built in 1913, and the addition to the west wing in 1928. Sometimes advertised as the world's largest log hotel, the building features a 100 feet long, 80 feet wide, and 80 feet high registration lobby. Lodge pole logs figure prominently in the construction of the Inn's outside walls and inside lobby balcony rails and supports. Guests who have stayed at Old Faithful Inn over the years include heads of governments, statesmen, financiers, and industrialists.

Built in 1881, the Queen’s Laundry Bath House was the first building constructed by the Federal government for public use in a national park. The building is a humble beginning to a policy of accommodating tourists in national parks, which would have tremendous influence on how parks were managed. The bath house is the oldest standing building constructed by the U.S. Department of the Interior for a national park function and the only building representing Yellowstone National Park’s early civilian administration from 1872-1886.

The Roosevelt Lodge Historic District is located on Lost Creek, 18 miles east of the Mammoth Hot Springs Headquarters area. The District is composed of 124 significant buildings related to lodging in Yellowstone National Park. The original lodge plan contained the lodge, constructed in 1919-1920, service buildings and 43 cabins. Over the years, additional cabins were built and other cabins were brought in from other areas in the park.

In 1918, the Director of the National Park Service recognized that the parks offered valuable educational advantages to universities and individual scholars and scientists. He promoted the use of the parks for field laboratory work and as a place for students to conduct studies of natural features at minimum expense. By 1921, the educational features of the Roosevelt Lodge area were being developed. Besides the area serving the park as a field laboratory, the National Park Service employed professor/naturalist, Dr. H.S. Conrad of Grinnell College to conduct daily nature field trips for the guests. Dr. Conrad also lectured and collected many botanical specimens for the park museum. These education examples are the predecessors of the extensive education programs found in the national parks today.

The lodge system developed in Yellowstone National Park during the 1920s and 1930s to serve the needs of the middle income guests. The new facilities augmented the hotel system which had its roots in the stagecoach eras. The lodge system, oriented toward automobile usage, maintained services and prices between those of hotels and housekeeping cabins. ''Roosevelt Camp'' was chosen as the site for the first lodge and would ultimately be the smaller of the lodges built. The Superintendent's Monthly Report for October 1919 states the proposition ''to make this camp something on the order of the 'dude ranch' of the West.''

This thematic study includes twelve post offices owned and administered by the U.S. Postal Service (USPS) throughout the State of Wyoming. These include the Basin, Greybull, Douglas, Lander, Torrington, Thermopolis, Buffalo, Kemmerer, Powell, Yellowstone, Evanston, and Newcastle Main Post Offices. The buildings represent a continuum of federally constructed post offices allocated to the state between the turn of the century and 1941. The buildings exhibit a variety of styles and sizes but maintain a common demeanor representative of the federal presence. All of the buildings were constructed from standardized plans developed from guidelines provided by the Office of the Supervising Architect in the Treasury Department. Variations in design styles reflect both the transition in the design philosophies of the Supervising Architect and the requirements developed in response to the Depression. These variations in design, as well as functions are also somewhat related to the communities in which they were placed and reflect the economic, political, and governmental context of those communities.