The National Museum of Natural History (NMNH) first opened to the public on March 17, 1910, as the new United States National Museum. The National Museum was first housed in what is now the Arts and Industries Building.
Grayscale postcard of two skeletons of horned dinosaurs on exhibit at the United States National Museum, now the National Museum of Natural History. The larger one is a Triceratops skeleton, and the smaller one is a Brachyceratops skeleton. The postcard is unused, but the message side has a printed note about the dinosaurs: "These skeletons of two extinct reptiles known as Horned Dinosaurs were discovered in the Cretaceous rocks of the West. Triceratops, the larger of the two specimens, shown, named for the three horns on its head, was about 20 feet long. With a head 6 feet in length it had the largest skull of any known reptile. The other skeleton, Brachyceratops, less in size than the skull of the Triceratops, is the smallest of North American horned dinosaurs. Both of these animals were plant eaters, living in the swamps of the western plains. They became extinct over 100,000,000 years ago."