The museum's collections total over 125 million specimens of plants, animals, fossils, minerals, rocks, meteorites, and human cultural artifacts. The museum is the second most popular of all of the Smithsonian museums. The museum is also home to about 185 professional natural history scientists — the largest group of scientists dedicated to the study of the natural and cultural history in the world.
The museum was established in 1910, with its building designed by Hornblower & Marshall. The building, designed in the neoclassical architectural style, was the first constructed on the north side of the National Mall, along Constitution Avenue, as part of the 1901 McMillan Commission plan.
Notable exhibits on the first floor (mall entrance) include the Kenneth E. Behring Family Hall of Mammals (exhibit design Reich+Petch Design International), which displays preserved pelts of mammals throughout the world, some of which were collected by former president Theodore Roosevelt. Also located on the first floor is the Hall of Dinosaurs. Adjacent to the dinosaur collection are exhibits which detail the evolution of life on Earth, going as far back as the Pre-Cambrian. The first floor also has many artifacts from non-western cultures.
The second floor contains the National Gem Collection, in the Janet Annenberg Hooker Hall of Geology, Gems, and Minerals which includes the Hope Diamond. Also on the second floor is the Orkin Insect Zoo. An IMAX movie theater, featuring films about wildlife, geography, natural history, and related topics, occupies space on both the first and second floors.
The ground floor contains a gift store, cafeteria, and an auditorium. The only notable exhibit on the ground floor is a collection of over 100 bird species which inhabit the Washington, D.C. metropolitan area.