The bombing of Pearl Harbor set off a chain of events that included the race to beat German scientists to build the atomic bomb. A tiny hamlet tucked away in the southern Appalachians proved an unlikely linchpin to win the race. The Manhattan Project required the combination of four secret sites—Clinton Laboratories, Y-12, K-25, and S-50—75,000 workers, and the nation’s finest scientists to create the Secret City, Oak Ridge. From the beginning, the effort was aided by the nearby University...