Course of the Colorado River into the Virgin River, which ran southward through what is now Overton Arm to join the Colorado River near the now-ghost town of St. Thomas, Nevada. At Hoover Dam, the Colorado turns due south through Black Canyon, a direction it will follow for the remainder of its course to the Gulf of California. It passes under the Mike O'Callaghan–Pat Tillman Memorial Bridge (Hoover Dam Bypass), the highest concrete arch bridge in the world, carrying U.S. Route 93 at a height of above the Colorado River. At the end of Black Canyon the Colorado widens into Lake Mohave, created by the
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