Built at the University of Chicago as Chicago Pile-1, the world’s first nuclear reactor was moved in 1943 to Site A in the Red Gate Woods and renamed CP-2. The site contained 10 tons of uranium metal, 42 tons of uranium oxide, and 472 tons of graphite, with the reactor core shielded by six inches of lead and four feet of wood. Under physicist Walter Zinn’s leadership, scientists at Site A conducted experiments in the small laboratory atop CP-2 and also built CP-3, the first water-cooled nuclear reactor. When the Atomic Energy Commission closed Site A in 1954, both reactors were dismantled and buried in a forty-foot-deep trench there. Beginning in the 1980s, the Commission and the Department of Energy responded to public concern by monitoring the area and working to neutralize toxic radioactive materials, and the site is now safe for public recreation.
