The quarry site at what is now Dinosaur National Monument was discovered in 1909 by Earl Douglass, a paleontologist from the Carnegie Museum in Pittsburgh, Pennsylvania. Douglass, whose specialty was fossil mammals, had been working in the Uinta Basin of northeastern Utah since 1907, collecting 40- million-year-old mammal fossils from the Eocene Uinta Formation. In hopes of finding dinosaur skeletons for display at the Carnegie Museum, Douglass was sent north by museum director Dr. W.J. Holland to the flanks of the Uinta Mountains, where uplift had exposed rocks from the age of dinosaurs. Among the layers of rocks exposed here is a rock unit or formation known as the.
The Morrison Formation originated approximately 150 million years ago as floodplain deposits. It was widespread, covering the area that is now Colorado, Wyoming, eastern Utah, northern New Mexico, parts of Montana and South Dakota, and the panhandle of Oklahoma. These sediments were deposited under conditions favorable for the burial and preservation of skeletal remains. Most of the Jurassic-age dinosaurs known from North America come from the Morrison Formation. This rock unit is named after Morrison, Colorado, a small town west of Denver where the first major discovery of Morrison dinosaurs was made in 1877.