John Wesley Powell was a pioneer American explorer, ethnologist, and geologist in the 19th Century. In 1869 he set out to explore the Colorado and the Grand Canyon. He gathered nine men, four boats and food for ten months and set out from Green River, Wyoming, on May 24. Passing through dangerous rapids, the group passed down the Green River to its confluence with the Colorado River (then also known as the Grand River upriver from the junction), near present-day Moab, Utah.