History of the Grand Canyon area stretched along a 278-mile (447 km) segment of the Colorado River from the southern border of Glen Canyon National Recreation Area to the eastern boundary of Lake Mead National Recreation Area. Grand Canyon National Park was designated a World Heritage Site on October 24, 1979. In 1935, Hoover Dam started to impound Lake Mead south of the canyon. Conservationists lost a battle to save upstream Glen Canyon from becoming a reservoir. The Glen Canyon Dam was completed in 1966 to control flooding and to provide water and hydroelectric power. Seasonal variations of high flow and flooding in the spring and
Steamboats of the Colorado River shared information about the conditions on the river above them. Robinson piloted the "Explorer" above the point reached by Johnson into the Black Canyon of the Colorado, where they struck a rock that damaged the boat, 40 miles above where Johnson reached. Ives named that rock "Explorer's Rock". While the "Explorer" was being repaired by his engineer, Ives, Robinson and the boat's mate, took their skiff over the next two days farther up the river exploring up through the Black Canyon and beyond to the vicinity of Fortification Rock. Next day, they went two miles farther to Las Vegas Wash,