It is listed on the National Register of Historic Places as U.S. Post Office-Miles City Main.

It was built in 1916 by Hiram Lloyd Co. Its design is credited to U.S. Supervising Architect Oscar Wenderoth.

[1] It is one of 18 Federally funded post offices built in Montana during 1900–1941, all of which survived until 1985 when they were reviewed for historic registry eligibility.

In the 1985 study, it was noted that a post office may have significance at a state level because it is a first or excellent example of a standardized design.

The Miles City post office, completed in 1916, is from a standardized design, and is actually nearly identical to the post office in Kalispell, Montana (completed in 1918); three others in the state are also excellent examples of standard designs.