Italian physicist Enrico Fermi managed the University of Chicago
reactor, called Chicago Pile 1 (CP-1). Nobel Prize-winner Fermi
had fled Fascist Europe. On the afternoon of December 2, 1942,
it happened. Under the abandoned west stands of Stagg Field, the
first controlled nuclear reaction occurred. Humankind had controlled
energy released from the nucleus of the atom.

CP-1 paved the way for Oak Ridge and Hanford to develop ways
of obtaining nuclear fuel for atomic weapons.