Dinosaur Skeleton Exposed in Dinosaur Quarry, Utah, 1922, Smithsonian Institution Archives, Large dinosaur skeleton in what is now Dinosaur National Monument being excavated by collectors from the Carnegie Museum of Natural History. The Carnegie Museum excavated in the area between 1909 and 1922, at which time they abandoned operations. The United States National Museum (now the National Museum of Natural History) began excavating in the area in 1923..