During the 1820s and 1830s, Euro-American mountain men ventured down and trapped parts of the Colorado. Famous personalities like Jedediah Smith, James Ohio Pattie, and Ewing Young searched for beaver along its banks, while another trapper, Denis Julien, left his inscription in Cataract Canyon.
Although these men explored sections of the river, it was not until 1869 and again in 1871-72, that the Colorado was fully mapped. John Wesley Powell's two expeditions, sponsored by the Smithsonian Institute and Congress respectively, charted the water's course from Green River, Wyoming, through the Grand Canyon and beyond. His ten- and eleven-man crews collected information and sailed their wooden boats down one of the most dramatic and roughest inland waterways in the United States.