McDowell Grove Forest Preserve is a 439-acre protected area in Naperville, Illinois, along the West Branch of the DuPage River. Established in 1930 from land bought from Alexander McDowell, it became a major Civilian Conservation Corps camp from 1934 to 1943, where crews built many early features, including bridges, a shelter, picnic grounds, a lagoon, and a limestone dam. After Pearl Harbor, the camp was adapted for wartime training by the U.S. Army Signal Corps and later the Office of Strategic Services. After the war, the land returned to forest preserve use, and today it provides recreation while retaining traces of its CCC past.