Red Gate Woods is part of a forest preserve within the Palos Division of the Forest Preserve District of Cook County, Illinois. Located within the preserve 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 nuclear reactor. After the initial tests, the reactor at Stagg Field at the University of Chicago was removed and reassembled at the Manhattan Project site in Red Gate Woods. Local residents reported encountering US Army MPs guarding the area during World War II but no one was aware of the true nature of the activities until long after the war. After further experiments and the shutdown of Pile 1, a huge hole was dug and the 2-story high reactor was pushed into it and buried. Other reactors were also built at the site and nuclear waste was buried there.