The Government Printing Office Warehouse (Building 4) was built in 1938. The building is made of reinforced concrete with Art Deco details, and has the capacity to hold 28 million pounds of paper.
The warehouse is on North Capitol Street, built near Union Station and linked to it by a railroad trestle, so that paper can be shipped to the GPO by train. From this warehouse, the paper can be conveyed to the main publishing building through a tunnel 30 feet below North Capitol St.
See also the 1903 Government Printing Office, and Building No. 3.