Question: where was the first us atomic bomb made

title: Manhattan Project
text: The discovery of nuclear fission by German chemists Otto Hahn and Fritz Strassmann in 1938 , and its theoretical explanation by Lise Meitner and Otto Frisch , made the development of an atomic bomb a theoretical possibility . There were fears that a German atomic bomb project would develop one first , especially among scientists who were refugees from Nazi Germany and other fascist countries . In August 1939 , Hungarian - born physicists Leó Szilárd and Eugene Wigner drafted the Einstein -- Szilárd letter , which warned of the potential development of `` extremely powerful bombs of a new type '' . It urged the United States to take steps to acquire stockpiles of uranium ore and accelerate the research of Enrico Fermi and others into nuclear chain reactions . They had it signed by Albert Einstein and delivered to President Franklin D. Roosevelt . Roosevelt called on Lyman Briggs of the National Bureau of Standards to head the Advisory Committee on Uranium to investigate the issues raised by the letter . Briggs held a meeting on 21 October 1939 , which was attended by Szilárd , Wigner and Edward Teller . The committee reported back to Roosevelt in November that uranium `` would provide a possible source of bombs with a destructiveness vastly greater than anything now known . ''