(1942–45) U.S. government research project that produced the first atomic bomb .
In 1939 U.S. scientists urged Pres. Los Alamos , N.M., and staffed by scientists headed by {{link=Oppenheimer, Julius Robert">J. Robert Oppenheimer . Production also was carried out at Oak Ridge, Tenn., and Hanford, Wash. The first bomb was exploded in a test at Alamogordo air base in southern New Mexico. By its end the project had cost some $2 billion and had involved 125,000 people.