U.S. Gov't agencies - Library of Congress: Geography & Map Reading Room
"Maps and atlases were among the first items acquired when the Library of Congress was established in 1800. It was not until 1897, however, when the Library of Congress moved into its own building, that a separate Hall of Maps and Charts was created to house the growing collection of 47,000 maps and 1,200 atlases. The division now occupies an area of 90,000 square feet in the Library's James Madison Memorial Building. The area is specifically designed and constructed to accommodate a variety of cartographic collections, library functions, and a professional and technical staff of 58 persons."