The City Walking Guide website points out that "The National Postal Museum is home to over 5.9 million items. This massive collection began with just one sheet of 10-cent Confederate postage stamps that was donated to the Smithsonian in 1886."
The site goes on to say that...
• Funding for the museum comes from the US Postal Service, The Smithsonian’s annual federal appropriation and private gifts from individuals and corporations. Most of the items in the museum are donations as well, which come from individuals and foreign governments.
• The current National Postal Museum didn’t open until July 30, 1993. Before then, the contents of the museum were kept in the Smithsonian’s Arts and Industries Building from 1908 to 1963. Between 1964 and the opening of the National Postal Museum, the collection was kept in the National Museum of American History.
• The National Postal Museum is massive at 75,000 square feet with a 90 foot high atrium. 23,000 square feet of that is for exhibitions and the rest is made up of a 6,000 square foot research library, museum shop and stamp store.
• William H. Gross founder of the investment firm PIMCO and an avid stamp collector, donated $8 million to the museum in September 2009. This money was gifted to go towards expansion of the museum, which will be called the William H. Gross Gallery and is expected to open in 2013.
To learn more about the National Postal Museum, click here.