The Colorado River was first inhabited by nomadic Native Americans, for about 8,000 years. They had large agricultural civilizations. These societies collapsed due to droughts, and poor land use habits/tactics. Europeans first entered the Colorado Basin in the 16th century. Explorers (mainly coming from Spain) claimed most of the land. Native Americans lived along the Colorado for about 2,000 years ago. They had the most sophisticated indigenous cultures. They mainly traded fur in the lower and headwaters parts of the river. It's believed that the Paleo-Indians of the Clovis and Folsom's culture were the first ever to arrive at the river over 12,000 years ago
John Wesley Powell (March 24, 1834--September 23, 1902) was a US solider, geologist, and more famously known as a American explorer of the American West. In 1869 he explored the Green and Colorado Rivers for three months. This was called the Powell Geographic Expedition. He was even the first known European to explore the Grand Canyon. He was also a director of the US Geological Survey, and he proposed many policies to evaluate the development of the arid West.