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 1,500,000 square feet (140,000 m2) with 325,000 square feet (30,200 m2) of exhibition and public space and houses over 1,000 employees.