[2] During World War II, Argonne Forest land leased to the Army Corps of Engineers became Site A, a research facility where experimental nuclear reactors built for the Manhattan Project helped in the development of the first nuclear weapons.

The Argonne Forest area is known to geologists as Mount Forest Island,[2] an area which, during the Last Glacial Period, formed a triangular island 6 miles (9.7 km) long and 4 miles (6.4 km) wide, rising 80 to 120 feet (24 to 37 m) above the waters of the surrounding ice-age Lake Chicago.

[5] The 6,600-acre Mount Forest Island area was, in 2021, designated an Urban Night Sky Place by the International Dark-Sky Association.

At this center one can learn things about nature of the surrounding area, and as well as the plants and animals that live there.

[5] Red Gate Woods is the burial place of Chicago Pile-1, the world's first nuclear reactor.

Constructed as part of the Manhattan Project, in 1943 the reactor was transferred from the University of Chicago to the Forest Preserve District for further experimental work.

[9] The burial site has a granite marker at its center and is perfectly safe to visit, but there is still some radioactive contamination underground and Tritium still leaches (at very low levels) into the nearby Des Plaines River.

Starting at the East entrance, there is a path used for hiking along the southern part of the lake, and it goes for about 3 miles.