The National Postal Museum, located opposite Union Station in Washington, D.C., United States, was established through joint agreement between the United States Postal Service and the Smithsonian Institution and opened in 1993. The Smithsonian's National Postal Museum is located in the historic City Post Office Building, which was constructed in 1914 and served as the Washington, D.C., post office from 1914 through 1986. The Museum occupies 100,000 square feet of the building with 35,000 square feet devoted to exhibition space.