River, western U.S. It flows from western Wyoming south into Utah, where it turns east to make a loop through the northwestern corner of Colorado.
Turning south in Utah, it enters the Colorado River in Canyonlands National Park after a course of 730 mi (1,175 km). Originally known as the Spanish River, it was renamed in 1824, probably for its colour, derived in places from green soapstone banks along its course.