The Smithsonian Institution, also known simply as the Smithsonian, is a trust instrumentality of the United States composed as a group of museums and research centers. It was founded on August 10, 1846, "for the increase and diffusion of knowledge".
The Smithsonian Institution is the world's largest museum and research complex, with 19 museums, 9 research centers, and affiliates around the world.
Termed "the nation's attic" for its eclectic holdings of 154 million items, the Institution's 19 museums, 21 libraries, nine research centers, and zoo include historical and architectural landmarks, mostly located in the District of Columbia. Additional facilities are located in Maryland, New York, and Virginia. More than 200 institutions and museums in 45 states, Puerto Rico, and Panama are Smithsonian Affiliates.
The Institution's 30 million annual visitors are admitted without charge. Its annual budget is around $1.2 billion, with two-thirds coming from annual federal appropriations. Other funding comes from the Institution's endowment, private and corporate contributions, membership dues, and earned retail, concession, and licensing revenue.
According to en.wikipedia