The Interior building is 7 stories with a basement (an additional floor between the 5th and 6th stories is devoted entirely to mechanical equipment). Above the central axis is a setback 8th story. The building is arranged into 6 east-west wings connected by a central north-south spine. This massing creates ten U-shaped courts, allowing each of the 2200 rooms an exterior exposure.
Secretary of the Interior Harold Ickes (who established the Historic American Buildings Survey, now a program of the National Park Service) was so involved with the design and construction of the Interior building that when the building opened, it was referred to as "Ickes new home." Ickes personally selected Waddy Butler Wood as architect and worked very closely with him to ensure comfort and efficiency in the innovative new building.
The Interior building featured a number of 'firsts' for Federal buildings: the first to have a central vacuum cleaning system, one of the earliest to be air-conditioned, and one of the first to incorporate a parking garage in the building.
The somewhat austere 'Moderne' exterior belies the interior's abundant artwork and ornamentation. The building's 3 miles of corridors are lined with many murals and sculpture. Six Native American artists painted more than 2200 square feet of murals.
The central corridor contains the Grand Staircase and has a checkered marble floor, bronze railings and a coffered plaster ceiling. A pair of marble bas reliefs by Boris Gilbertson adorn the walls: one of moose and the other of buffalo. The buffalo motif is found throughout the building including in the Departmental Seal and on the doorknobs of the Secretary of the Interior's Executive Suite. The Executive Suite has oak paneling with a marble fireplace. Besides offices, the building contains an auditorium, museum, Indian arts and crafts gift shop, library, post office and gymnasium-all part of the original design.
The U.S. Department of the Interior is located at 18th, 19th, C and E Streets, NW. The building is open to the public Monday through Friday from 8:30 am to 5:00 pm.