Chicago

The 1920s brought notoriety to Chicago as gangsters, including the notorious Al Capone, battled each other and law enforcement on the city streets during the Prohibition era. The 1920s also saw a major expansion in industry. The availability of jobs attracted African Americans from the South. Arriving in the tens of thousands during the Great Migration, the newcomers had an immense cultural impact. It was during this wave that Chicago became a center for jazz, with King Oliver leading the way.[16] In 1933, Mayor Anton Cermak was assassinated while in Miami with President Franklin D. Roosevelt.

In the late summer of 1942, during World War II, Chicago held a practice black-out. According to one witness, "the sirens sounded, the lights went out while airplanes flew overhead to spot violators". After about 30 minutes the beacon on top of the Palmolive Building came back on and the lights were quickly restored.[17]

On December 2, 1942, physicist Enrico Fermi conducted the world’s first controlled nuclear reaction at the University of Chicago as part of the top-secret Manhattan Project.