Chicago Pile-1 (CP-1) was the world’s first artificial nuclear reactor. CP-1 was built on a rackets court, under the abandoned west stands of the original Alonzo Stagg Field stadium, at the University of Chicago. The first artificial, self-sustaining, nuclear chain reaction was initiated within CP-1, on December 2, 1942. The site was designated a National Historic Landmark in 1965 and was added to the newly created National Register of Historic Places a little over a year later. The site was named a Chicago Landmark in 1971. It is one of the four Chicago Registered Historic Places from the original October 15, 1966, National Register of Historic Places list.
On December 2, 1942, CP-1 was ready for a demonstration. Before a group of dignitaries, a young scientist named George Weil worked the final control rod while Fermi carefully monitored the neutron activity. The pile reached the critical mass for self-sustaining reaction at 3:25 p.m. Fermi shut it down 28 minutes later.