Dinosaur National Monument

On 17 August 1909, Earl Douglass of the Carnegie Museum found eight vertebrae of an Apatosaurus weathering out of a sandstone ridge. That was the first skeleton dug from what became the Carnegie Quarry, and six years later, on 4 October 1915, the ground around it was declared a national monument.

The quarry wall is the thing to see. The bones sit in a sandstone and conglomerate bed of the Morrison Formation, laid down by rivers about 150 million years ago in the Jurassic. Animals died, a river system carried and dumped them together, sediment buried the pile, and it hardened into rock. Then the mountain building that raised the Uinta Mountains during the Laramide orogeny tilted the whole bed on end, and erosion cut into it. The result is a slab of Jurassic riverbed standing at an angle with the bones still in place.

The monument holds over 800 palaeontological sites and has produced Allosaurus, Deinonychus, various sauropods, and Abydosaurus, whose holotype is a nearly complete skull with the lower jaw and the first four neck vertebrae, out of the base of the Mussentuchit Member of the Cedar Mountain Formation. The monument was greatly expanded in 1938 to take in the wider landscape, sitting on the Colorado and Utah border where the Green and Yampa rivers meet.

Human history runs deep here too. The Fremont people lived in this country before the fourteenth century, sheltering under rock overhangs and in small villages, growing corn, beans and squash, and they left petroglyph panels that you can still visit at McKee Springs in the Rainbow Park area. That corner is about 30 miles from the Quarry Visitor Center on unpaved roads which are impassable when wet, so check conditions before committing to the drive.

In April 2019 the International Dark-Sky Association designated the monument an International Dark Sky Park. Come for the bones, stay for the sky.