Located on the Sacramento River just outside Redding, CA, Shasta Dam is the second largest dam in the United States. It is 602 feet high, 883 feet thick at the bottom, and the 400 foot spillway is the largest manmade waterfall in the world. Built as part of the Central Valley Project, construction began in 1938 and was completed in 1945, after a total of 6,270,000 cubic yards of concrete had been poured.