The Dinosaur Diamond Prehistoric Highway is a 512-mile loop in eastern Utah and western Colorado, with three-quarters of the route in Utah. The Colorado segment was designated the Dinosaur Diamond Scenic and Historic Byway by the Colorado Transportation Commission on October 27, 1997, and the Utah segment was designated the Dinosaur Diamond Prehistoric Highway by the Utah State Legislature in 1998. Tyrannosaurus Rex was one of the largest meat-eating dinosaurs that ever lived, and its thick, heavy skull and 4-foot-long jaw were built for maximum bone-crushing action. Apatosaurus, also known as Brontosaurus, was a sauropod dinosaur that lived during the Jurassic Period, 155.7 to 150.8 million years ago, across territory including Colorado, Utah, Wyoming, Oklahoma, and Mexico, and it was first discovered in 1877 in the Rocky Mountains of Colorado.