The Alex Halone property is located in a residential area of Thermopolis that is close to the Big Horn River. Halone, a skilled stone mason who emigrated from Finland, utilized his talents in the construction of his house in 1909-1910 and later in the construction on the property of a garage, picnic shelter, barn/garage, fish pond bridge, well, outdoor grill, stone walkways and walls, and log sauna. Mr. Halone's imaginative combination of different types of stone, including river rock, travertine, flagstone, sandstone and granite, is exhibited on the buildings he constructed for personal use as well as other examples of his work in the Thermopolis area. The Halone property illustrates the talents of an energetic stone mason who continued to add to his personal property through the years. Similar to other craftsmen, Halone used his own house and out buildings to showcase his talent. Halone shared his knowledge with his son Eugene and worked with his grandsons teaching them stone masonry. Through the years, Mr. Halone remodeled the house to fit the needs of his family as well as the community. When housing was limited in Thermopolis during the 1920s, Halone altered his house and converted rooms into separate apartments to accommodate new immigrants and others in need of housing. The log sauna, constructed by Alex and Eugene Halone with assistance from Lauri Suikaonen in 1946-51, is an unusual sight in Wyoming. Only one other Finnish sauna has been identified in the state and it does not have the distinctive appearance of Alex Halone's sauna. The Halone sauna is an exceptionally significant part of Wyoming's architectural folk heritage.

The Plaza Inn is significant as the sole remaining hotel/apartment building left in Hot Springs State Park. It represents the beginning of commercialization in the State Park which started in the early 1900s. At one time there were over six facilities to provide the sick and ailing access to the healing waters of the Big Spring, the most famous being the Carter Hotel and Sanitarium which was demolished in 1966. James McLaughlin, United States Indian Inspector, reported to the Department of the Interior in 1896, his findings and opinions on what is now known as the Hot Spring State Park. ''The water of this spring is said to possess wonderful curative properties and to be very beneficial for rheumatic and other ailments, and although the temperature is 132 degrees it is not unpleasant to drink, and with salt and pepper added tastes very much like fresh chicken broth.'' (Senate Document No. 247, 54th Congress, 1st Session.) The park was purchased by the government from the Shoshone and Arapahoe Indians in 1897, and the Hot Spring State Reserve was formed.

The commercial development of Hot Springs State Park Reserve began soon after a small settlement located at the mouth of the Owl Creek moved to the Hot Springs. Thermopolis (Greek meaning ''Hot City'') sprang to life with tourist activity when a series of hotels were constructed in the new state park. The last hotel was built by brick layer James Callaghan beginning in November 1917. By June of 1918 the Callaghan Apartments were ready for guests. Mr. Callaghan and his wife Hazel ran the hotel a short time. The two story brick structure originally housed 70 rentable rooms, divided into fourteen sections, each hall containing a common bathing room at the end of each corridor. In 1921 Dr. P. W. Metz purchased shares in the Callaghan Apartment Company, Inc. and ownership was legally transferred. Dr. Metz renamed the hotel Plaza Apartments and Hotel and it has been referred to as the Plaza since then. Ownership has changed many times, but the business at hand has always been to provide guests of the Plaza access to the mineral baths.

Thermopolis is located along the Northern Burlington railroad line, at the mouth of Wind River Canyon in northwest Wyoming, approximately 120 miles southeast of Yellowstone National Park. Buildings in Downtown Thermopolis Historic District are located in a compact area on the main street, Broadway, and on Fifth Street, which runs perpendicular to Broadway and forms the eastern boundary of the District. Broadway Street itself provides the setting for these buildings in much the same way today as it did in yesteryear. Built double-wide to accommodate teams of up to 16 mules or horses transporting freight, today, the same four-lane street is befitting for automobile traffic and ample parking. The buildings in the district are all commercial, and have both architectural and historical significance. They were constructed between 1898 and 1923 and portray a Victorian, transitional turn-of-the-century commercial architecture. Some buildings reflect a very elaborate Victorian style, while others represent the skills of a local bricklayer by their similar decorative bricked patterns on the second floors. Still others exemplify the work of one of the local stonemasons active at the turn of the century. Thus, the entire district is a representation of the different skills and materials available throughout the town's history.

Thermopolis was a planned community which began shortly after its site was sold to the U.S. Government by the Shoshoni and Arapahoe Indian Tribes, who had previously owned the property as part of their reservation. The old town, Andersonville, was located at the mouth of Owl Creek. After the Treaty of 1896 was ratified by Congress, this town picked up and moved to the present site, which had been platted and surveyed, provision being made for the growth of a large city. The town was organized under townsite laws, and the title was issued to corporate authorities, in trust. The present day town reflects the insight of its forefathers, both in its layout of streets and sidewalks, and in its proximity to the Big Horn Springs, often claimed to be the largest producing hot mineral springs in the world.

The forty bridges in this thematic study are the best of their types which were still in use on the state and county road systems in Wyoming when the study was completed in 1982. Selected from a statewide survey of all functional vehicular trusses and arches using a specific evaluation criteria and methodology, most represent superlatives of their generic engineering types (i.e. truss configuration and connection types) while typifying bridgebuilding and transportation trends in the state. All were built in the first three decades of the twentieth century (1905-1935). Although bridges were put up during the earlier periods of overland wagon emigration, they had not begun to proliferate in the state of Wyoming until the early twentieth century with the emergence of the automobile as a principal form of transportation. All the listed bridges display a remarkable homogeneity of construction and operational histories. Generally, county-built trusses were contracted through competitive bidding among several Midwestern bridge erectors and built from standardized designs using prefabricated components. After creation of the Wyoming Highway Department in 1917, the role of the counties in truss bridge construction diminished. The later highway department bridges were typically designed from standard plans maintained by the department and built by local contractors from components fabricated in the same Midwestern foundries.

One feature that all steel truss bridges shared was their versatility. Quickly erected, they could also be dismantled and moved if necessary. Many county road bridges in Wyoming had begun service as railroad bridges, sold or given to the counties as obsolete structures. Similarly, early highway bridges which had become unsuitable to handle increasing volumes of traffic were sometimes replaced with new trusses, with the older bridges demoted to places along less traveled roads. After World War II, new trussbuilding was rare in Wyoming. Today trusses have been largely superseded by more sophisticated engineering designs and are seldom erected. The remaining highway and roadway truss bridges are remnants of past technologies, whose numbers are continually dwindling through attrition.

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.