Caption:
Walter Zinn at Chicago Pile-1. Chicago Pile-1 (CP-1) was the world's first man-made nuclear reactor. CP-1 consisted of 45,000 graphite bricks stacked in 587 layers. The first self-sustaining nuclear chain reaction was initiated in CP-1 on December 2, 1942 at its site underneath the University of Chicago's Stagg Field football stadium. The site is now a National Historic Landmark. Walter Zinn (1906-2000) was a Canadian-born nuclear physicist who worked on the Manhattan Project, was a director of the Argonne National Laboratory from 1946-1956, and developed and built several new reactor designs.