For a couple of years scientists were trying to convince FDR of the need to work on an atomic bomb. FDR and his scientists did not think it possible and so deemed it not necessary for funding. Finally in 1939 Albert Einstein sent a letter, hoping his name would lend some weight, which it did. Now with some funding on Dec 2, 1942, Enrico Fermi, in a squash court under the football stadium at the University of Chicago, demonstrated it was possible to produce a nuclear chain reaction. The Manhattan Project was established shortly after.
Historically Speaking 