The National Archives and Records Administration has two buildings, Archives I (near the National Mall in Washington, DC) and Archives II (College Park, MD). They house about 10 billion historical records.
Interesting links include:
A news story about The National Archives’ treasure hunters; The official homepage; A Wikipedia article on the NARA; NARA’s online exhibits; and the American Memory Historical collections, including Baseball Cards, 1887-1914 and Early Films of New York, 1898-1906.
*the above image is of Richard Nixon’s resignation letter in the American Originals exhibit, shown here.