The Postal History Foundation
According to its website, "The Foundation is a hub of postal research and education in the southwest. While it maintains the largest and one of the finest facilities dedicated to postal history in the western United States, the Foundation is also the only philatelic museum that operates an extensive youth education program."
It goes on to say, "The Peggy J. Slusser Library houses a collection of more than 25,000 books, journals, US Post Office and United States Postal Service (USPS) publications. These provide scholars with a worldwide range of philatelic literature. The collection maintains a special emphasis on the United States, and is a rich source of Civil War literature, memorabilia and ephemera. The library is recognized as one of the top 42 libraries in the United States as best architecturally designed for users."
For more on the Postal History Foundation, click here.