Red Gate Woods is a forest preserve section within the Palos Forest Preserve, a division of the Forest Preserve District of Cook County, Illinois. It is located near where the Cal-Sag Channel meets the Chicago Sanitary and Ship Canal. In the woods is the original site of Argonne National Laboratory and the Site A/Plot M Disposal Site, which contains the buried remains of Chicago Pile-1, the world's first artificial nuclear reactor.

Chicago Pile-1 (CP-1) was the world's first artificial nuclear reactor. On 2 December 1942, the first human-made self-sustaining nuclear chain reaction was initiated in CP-1 during an experiment led by Enrico Fermi. The secret development of the reactor was the first major technical achievement for the Manhattan Project, the Allied effort to create nuclear weapons during World War II. Developed by the Metallurgical Laboratory at the University of Chicago, CP-1 was built under the west viewing stands of the original Stagg Field. Although the project's civilian and military leaders had misgivings about the possibility of a disastrous runaway reaction, they trusted Fermi's safety calculations and decided they could carry out the experiment in a densely populated area. Fermi described the reactor as "a crude pile of black bricks and wooden timbers".