Construction of Hanford's B Reactor began in June 1943, and the reactor was loaded in September 1944. As the first full-scale nuclear reactor in the world, it was the first to demonstrate the practicality of producing large quantities of plutonium and successfully demonstrated large-scale energy generation using the fission process. It was a major milestone in the United States Atomic Energy Program. Constructed by E.I. du Pont de Nemours Co., it was designed by Enrico Fermi, John A. Wheeler, Eugene Wigner, and staff. It was designated a Nuclear Historic Landmark in October 1992 by the American Nuclear Society and recognized in 1994 as the world's first full scale nuclear reactor.