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
Agriculture in the Southwestern United States any other region of the United States, so it is warmer on average. There are two main physiographic regions which Arizona is a part of. North and east Arizona is part of the Colorado Plateau, and the Basin and Range is in southern and western Arizona. The Colorado Plateau is a flat, elevated land of soft sedimentary rock about 5,000 to 9,000 feet above sea level. Rivers cut deep canyons and gorges into the plateau, the largest of which is the Grand Canyon of the Colorado River, which is in the northwest corner of Arizona. There are also scattered mountains