1Tread lightly in Red Gate Woods, a forest preserve near southwest suburban Lemont: A stone monument in a meadow marks the spot where the University of Chicago buried waste from the world’s first self-sustaining nuclear chain reaction—the school’s main contribution to the Manhattan Project.

2A turreted mansion at 48th and Ellis in Kenwood served as a detention center for “enemy aliens”—natives of Axis countries who had immigrated to the United States before the war but didn’t pass muster before a civilian alien hearing board. A few Italians were held there, but most of the roughly 20 detainees were German.

3During a trip to Germany in 1941, Lane Tech grad Herbert Hans Haupt was recruited to work for his native country’s intelligence agency, the Abwehr. A U-boat covertly returned Haupt and other spies to the United States, dropping them at a Florida beach; from there, he took a train back to Chicago. When two members of the group defected to the American side and became informers, they betrayed Haupt, and he was captured, tried, and executed.

4The government relocated nearly 20,000 Japanese Americans to Chicago to work in wartime factories. In a grim twist, documentary producers believe some may have been sent to the Dodge aircraft plant in West Lawn to build engines for the B-29 Superfortress—the same type of plane that would eventually drop the atomic bombs on Hiroshima and Nagasaki.

A City at War: Chicago premieres November 9 on WTTW.