The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. With free admission and open doors 364 days a year, it is the third most visited museum in the world, the most visited natural history museum in the world, and the most visited museum (of any type) in North America. Opened in 1910, the museum on the National Mall was one of the first Smithsonian buildings constructed exclusively to hold the national collections and research facilities. The main building has an overall area of 1,500,000ft2 with 325,000ft2 of exhibition and public space and houses over 1,000 employees.The museum's collections contain over 126 million specimens of plants, animals, fossils, minerals, rocks, meteorites, human remains, and human cultural artifacts. With 8 million visitors in 2013, it is the most visited of all of the Smithsonian museums and is also home to about 185 professional natural history scientists — the largest group of scientists dedicated to the study of natural and cultural history in the world.History1846–1911The United States National Museum was founded in 1846 as part of the Smithsonian Institution. The museum was initially housed in the Smithsonian Institution Building, which is better known today as the Smithsonian Castle. A formal exhibit hall opened in 1858. The growing collection led to the construction of a new building, the National Museum Building (known today as the Arts and Industries Building). Covering a then-enormous 2.25acre, it was built in just 15 months at a cost of $310,000. It opened in March 1881.