Most native peoples that inhabit the basin today are descended from other groups that settled in the region beginning about 1,000 years ago.
Europeans first entered the Colorado Basin in the 16th century, when explorers from Spain began mapping and claiming the area, which later became part of Mexico upon its independence in 1821.
The environmental movement in the American Southwest has opposed the damming and diversion of the Colorado River system because of detrimental effects on the ecology and natural beauty of the river and its tributaries.
During the construction of Glen Canyon Dam, environmental organizations vowed to block any further development of the river, and a number of later dam and aqueduct proposals were defeated by citizen opposition.
Large engineering works began around the start of the 20th century, with major guidelines established in a series of international and U. interstate treaties known as the "Law of the River". Most of the major dams were built between 19; the system keystone, Hoover Dam, was completed in 1935.
The Colorado is now considered among the most controlled and litigated rivers in the world, with every drop of its water fully allocated.
At Morelos Dam, the entire remaining flow of the Colorado is diverted to irrigate the Mexicali Valley, among Mexico's most fertile agricultural lands.Several expeditions charted the Colorado in the mid-19th century – one of which, led by John Wesley Powell, was the first to run the rapids of the Grand Canyon.American explorers collected valuable information that was later used to develop the river for navigation and water supply.As demands for Colorado River water continue to rise, the level of human development and control of the river continues to generate controversy.For the first 250 miles (400 km) of its course, the Colorado carves its way through the mountainous Western Slope, a sparsely populated region defined by the portion of the state west of the Continental Divide.