Inside the Secret Cities That Created the Atomic Bomb

Built by the U.S. Army Corps of Engineers at rapid speed beginning in 1942, the instant wartime cities of Oak Ridge, Tennessee; Hanford/Richland, Washington; and Los Alamos, New Mexico, revolved around military research. They held laboratories and sprawling industrial plants, but also residential neighborhoods, schools, churches, and stores—war workers had personal lives and families, after all. At their peak in 1945, the three cities had a combined population of more than 125,000.

Their research facilities later morphed into national laboratories. But during the war, none of the cities appeared on any maps: They were the top-secret centers of the Manhattan Project, the U.S. military’s initiative to develop nuclear weapons before the Nazis got there first. The project achieved bitter success in August 1945, when the U.S. dropped atomic bombs on Hiroshima and Nagasaki in Japan, instantly killing 150,000 people. Japan surrendered several days later, effectively ending the war, although historians still disagree about whether the use of nuclear weapons hastened the end.