The secret cities where the atomic bomb was built
The cities, which also served as testing grounds for new architectural principles, were Los Alamos in New Mexico, Oak Ridge in Tennessee and Hanford/Richland in Washington state.
It was all done in secret. They weren't on any maps, and almost none of the residents knew they were working on a new type of bomb, only some kind of war effort. For a casual observer, these cities were normal places with the occasional oddity: Every baby born in Los Alamos, for example, had a P.O. box in Santa Fe listed as their birth place.
But on August 6, 1945, when the bomb nicknamed "Little Boy" was dropped on the Japanese city of Hiroshima, the true nature of these cities was revealed to the world -- and to the people who lived in them.