Dinosaur National Monument spans the Utah-Colorado border where the Green and Yampa rivers meet, combining major paleontological resources with canyons, archaeological sites, and recreation lands. It began after Earl Douglass discovered dinosaur bones here in 1909, leading to federal protection in 1915 and a large expansion in 1938. Its best-known feature is the Quarry Exhibit Hall’s Wall of Bones, where thousands of Jurassic fossils remain embedded in tilted rock of the Morrison Formation. The monument also preserves evidence of Fremont occupation and became a landmark in conservation history when opposition to the proposed Echo Park Dam helped secure stronger protections for national parks and monuments.