History of the National Park Service and multi purpose river basin development programs like the Tennessee Valley Authority which began in the 1930s and spread to river valleys in all parts of the country after World War II. Lake Mead was the first National Recreation Area. The Boulder Canyon Project Act, passed in 1928, authorized the Bureau of Reclamation to construct Hoover Dam on the Colorado River. Work began in 1931 and the dam, highest in the Western Hemisphere, was completed in 1935. The next year, under provisions of an agreement with the Bureau of Reclamation, the National Park Service assumed responsibility for all recreational activities
Course of the Colorado River Topock Marsh in Topock Gorge and widens into Lake Havasu, formed by Parker Dam. Lake Havasu provides recreation as well as the home of the retired U.K. London Bridge in Lake Havasu City, Arizona, now the New London Bridge. Near Parker Dam are the first two major diversions of the lower Colorado: the Colorado River Aqueduct, which travels west to Los Angeles and San Diego, California; and the Central Arizona Project, which sends water east towards Phoenix and Tucson, Arizona. The intermittent Bill Williams River joins the Colorado from the east in Lake Havasu, just above Parker Dam. The river