The Smithsonian Institution is an educational foundation chartered by Congress in 1846 that maintains most of the nation's official museums and galleries in Washington, D.C. The U.S. government partially funds the Smithsonian, and its collections are open to the public free of charge. The Smithsonian's locations had a combined total of 30 million visits in 2013. The most visited museum is the National Museum of Natural History on the National Mall. Other Smithsonian Institution museums and galleries on the mall are: the National Air and Space Museum; the National Museum of African Art; the National Museum of American History; the National Museum of the American Indian; the Sackler and Freer galleries, which both focus on Asian art and culture; the Hirshhorn Museum and Sculpture Garden; the Arts and Industries Building; the S. Dillon Ripley Center; and the Smithsonian Institution Building (also known as "The Castle"), which serves as the institution's headquarters.