This beautifully scaled and finely detailed building, with exceptionally fine interiors, is a tour de force of restrained neo-classical design and an outstanding example of American civil architecture. The design of the building, based on a traditional Renaissance palazzo, is the first use of the Italianate style for an important public building in America; it also was the first use of marble for one of Washington’s public buildings. Both architect Robert Mills and his contemporaries considered the building his masterwork.
In the late 1890s, upon completion of the new Post Office building on Pennsylvania Avenue (now known as the Old Post Office), Congress transferred the building to the Secretary of the Interior. After this transfer, it housed the General Land Office and the Bureau of Education. One of the government’s first central power, heating, and lighting plants, located in the basement, served the Pension Office, the Patent Office, Court House, Court of Appeals, and Bureau of Mines. The Interior Department's occupancy continued until 1917, when its new offices were completed at 18th and F Streets (see Interior Department Offices). After the U.S. entered World War I, the Army operated the National Selective Service Board from the building, and in 1919, General John J. Pershing occupied the building while preparing his final reports as Commander-in-Chief of the American Expeditionary Forces. After Pershing’s departure in 1921, the Tariff Commission first occupied part of the building, and from 1940 until about 1990 it occupied most of the structure.
Although built in sections, the exterior is a harmonious composition, articulated by Corinthian pilasters and columns, with only minor differences in detail. The Mills wing is of New York marble, and the Walter section of Maryland marble. The keystone above the 8th Street carriageway entrance displays a carved female head representing Fidelity, and bas-reliefs in the spandrels of winged figures bearing a thunderbird and locomotive, symbolizing Electricity and Steam, respectively. These were sculpted by Guido Butti in 1856. Outstanding interior features in the Mills wing include barrel-vaulted corridors with plaster friezes on the main floor, two graceful curved cantilevered granite stairways in domed alcoves, and the vaulted third floor main hall with a domed central skylight.
DC Inventory: November 8, 1964 (Joint Committee on Landmarks)
National Register: March 24, 1969
National Historic Landmark: November 11, 1971