Secret A-Bomb Factories
In 1939 a group of scientists - Albert Einstein among them - warned President Roosevelt, of the possibility that Hitler's Germany might be close to producing an atomic bomb. Roosevelt issued an order - whatever it takes, the US has to be the first to develop an atomic bomb. And within three years they were well on their way to creating a hidden world of secret cities and classified nuclear facilities, built inside America. 400,000 people were part of it - though only a handful really knew the truth.