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
Floods in the United States: 1901–2000 which was recorded at on July 1. The Colorado, which is usually dry at the mouth due to extensive diversions, reached the Gulf of California for the first time since the 1960s. Due to a spillway design error at Glen Canyon coupled with the relentless flooding, the dam at Glen Canyon very nearly failed, which would have emptied Lake Powell (the second-largest man-made lake in the US) and flooded out the entire lower valley of the Colorado River, cutting off water supplies to millions of people. By August as the water finally began to recede, the dam held, though only