The Smithsonian Institution, established in 1846 "for the increase and diffusion of knowledge", is a group of museums and research centers administered by the United States government. Termed "the nation's attic"for its eclectic holdings of 137 million items, the Institution's Washington, D.C. nucleus of nineteen museums, nine research centers, and zoo many of them historical or architectural landmarks is the largest such complex in the world. Additional facilities are located in Arizona, Maryland, New York City, Virginia, Panama and elsewhere, and 168 other museums are Smithsonian affiliates. The Institutions's thirty million annual visitors are admitted without charge; funding comes from the Institution's own endowment, private and corporate contributions, membership dues, government support, and retail, concession and licensing revenues. Institution publications include Smithsonian and Air & Space magazines.