 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 nuclear reactor.This section of the forest preserves, then code named Argonne (after, Forest of Argonne) was leased by county commissioners to the Manhattan Project (and later Argonne Laboratory) in the 1940s and 1950s.After its initial tests, the reactor at Stagg Field at the University of Chicago was removed and reassembled at the Metallurgical Laboratory site in these woods ("Site A").