The world’s most infamous clown, John Wayne Gacy, went on trial after he murdered 33 young men in Cook County, Illinois.
Source
The world's first self-sustaining nuclear chain reaction happened in Chicago Pile-1 at the University of Chicago. It was overseen by Enrico Fermi.
Paul Galvin and his brother Joseph founded Motorola as the 'Galvin Manufacturing Co.' in Chicago, Illinois.
The first Mormon Pioneers left their homes in Nauvoo, Illinois, and began the long trek to the Salt Lake Valley.
Prolific killer John Wayne Gacy was given the death sentence for the murder of 33 young men and boys.
The Cherry Mine disaster in Illinois killed 259 miners in a coal mine fire.