This block long building was designed under the direction of the Acting Supervising Architect for the U.S. Treasury Department, James Wetmore. Colossal Ionic order columns unify the upper two stories of this limestone-veneered example of the Neo-Classical Revival style. This imposing symbol of the federal government was completed in 1929 at a cost of nearly $1 million. The Post Office was constructed as the first piece of a grand scheme by famed urban planner John Nolen to turn the street into a civic boulevard leading from the State Capitol to the lake's edge. Although the State Office Building and the City/County building were both built later on sites intended for public buildings, Nolen's vision of Neo-Classical style buildings lining the street was not brought to fruition.

While the exterior of the building has had minimal alterations, much of the interior of the first floor and basement were remodeled when the building was converted to city offices in 1980. However, the second floor, including the former courtroom belonging to the Western Wisconsin Branch of the US Court, retains many original features, including wood paneling, tile floors and marble baseboards.

The building is now known as the Madison Municipal Building and is open to the public during normal business hours.