Seeking a remote location for top secret nuclear experiments, the U.S. Army Corps of Engineers built the Site A research facility on land leased from the Cook County Forest Preserve in Red Gate Woods. Along with research labs and reactor control rooms, the complex included a guard house, dog shelter, library, cafeteria, dormitory, and recreational spaces. The scientists who lived and worked there throughout World War II maintained a strict code of silence because their discoveries were critical to the success of the U.S. military's atomic program. After extensive clean-up, the site is safe for public recreation.