was the code name for the US effort during World War II to produce the atomic bomb. It was named for the Manhattan Engineer District of the US Army Corps of Engineers, since much of the early research was done in New York City. It was top-secret engineering and industrial project in the United States during World War II, started by refugee physicists in the United States, the program was slowly organized after nuclear fission was discovered by German scientists in 1938, and many US scientists were scared that Hitler would attempt to build a f ....