The National Postal Museum was created in 1990 as the result of an agreement between the Smithsonian Institution and the United States Postal Service. Under this agreement the Smithsonian installed its National Philatelic Collection in space provided by the Postal Service in the Washington City Post Office, designed by Daniel Burnham, completed in 1914, renovated, and reoccupied in 1991. Both the Smithsonian and the Postal Service contribute to its operations.

Curators at the National Postal Museum research the history of the American postal system and collect American postage, special stamp editions of famous individuals or subjects, postal stationery, Post Office equipment and uniforms, and foreign stamps primarily for what they show about American history.

Herbert Ridgeway Collins served as the first Director of the National Postal Museum, 1990-1991, and was succeeded by James H. Bruns, Deputy Director, 1990, and Director, 1991- 2001. Allen Kane succeeded him, serving 2002- .