Black Canyon of the Colorado Black Canyon of the Colorado The Black Canyon of the Colorado is the canyon on the Colorado River where Hoover Dam was built. The canyon is located on the Colorado River at the state line between Nevada and Arizona. The western wall of the gorge is in the El Dorado Mountains, and the eastern wall is in the Black Mountains of Arizona. The canyon formed about 15 million years ago during the Miocene Basin and Range uplift. Black Canyon gets its name from the black volcanic rocks that are found throughout the area. Just south of the Hoover Dam on
Gold mining in the United States at the Moss mine at Oatman. In 2006, all of Arizona's gold production came as a byproduct of copper mining. Spanish prospectors found gold in the Potholes district between 1775 and 1780, along the Colorado River, in present Imperial County, California, about ten miles northeast from Yuma, Arizona. The gold was recovered from dry placers. Other placer deposits on the west bank of the Colorado River were quickly found, including the Picacho and Cargo Muchacho districts. Placer gold deposits were found at San Ysidro in San Diego County in 1828, San Francisquito Canyon and Placerita Canyon in Los Angeles County