The City of Lander has played a major role in the settlement and development of west-central Wyoming since the late 1860s. It is associated with several major frontier themes: the Great 19th Century Westward Migration, due to its close proximity to the Oregon Trail; military explorations and Indian relations in the formation of the Lander Cut-Off in 1859 and the Wind River Indian Reservation in 1868; the nearby South Pass mining boom; the establishment of major transportation and communication routes to serve the Wind River Reservation; the arrival of the railroad in 1906; cattle and sheep ranching; the early 20th century oil industry; and Lander's development into a major commercial center in the Lander Valley. Euro-American settlement had begun in the Lander Valley shortly after the discovery and development of significant gold deposits in the South Pass area in 1867.

The Lander commercial district grew from a post office and several businesses established as early as 1875. The district experienced several major building booms, progressing from log and wood frame buildings to more substantial two-story brick and stone masonry edifices with highly ornamental facades. The majority of the remaining commercial buildings within the district date from the late 1880s-early 1890s boom. Despite subsequent boom and bust periods brought on by the wildly fluctuating energy and ranching industries, Lander has endured as a stable commercial and social center for the Lander Valley.

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.