In the early 1800s the waters of the Green River nourished an abundant beaver population. Valued for their pelts, beavers began to be trapped as a marketable commodity. While small numbers of trappers and Natives hunted in the Green River basin, there was no major impact on the environment, but in 1825 William Henry Ashley revolutionized the area's fur trade. He held annual rendezvous at points along the Green River where trappers would exchange their pelts with traders from St. Louis, making the business more efficient.

The rendezvous system was an enormous business success, but it came at a cost. It decimated the beaver population, altered relationships between traders and Native Americans, and exacerbated international rivalries in the area. Within 15 years the organized commercial fur trade came to an end. It had transformed the natural environment and human society along the Green River, and it had paved the way for white emigration to and through the area.

The fur trade, much romanticized in literature and the popular imagination, enabled people both to flee the constraints of established society in the East and to spread the social institutions of the growing young nation. The fur trade is thus a symbol of escape and expansion, providing a metaphor for the larger Colorado River experience.

"Beaver and other kinds of game become every year more rare; and both the hunters and Indians will ultimately be compelled to herd cattle, or cultivate the earth for a livelihood; or in default of these starve."

Warren Angus Ferris, 1835