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Paddy "the Bear" Ryan, leader of the Valley Gang, is killed by Walter "The Runt" Quinlan.
February 3 – Chicago labor racketeerMaurice Enright is killed. Timothy D. "Big Tim" Murphy is suspected in his slaying, but is released for lack of evidence. Although suspected by authorities to have involved the Torrio-Capone organization, Chicago labor union racketeer James Vinci is eventually convicted of his murder.
May 11 – Chicago gambling racketeer James "Big Jim" Colosimo is killed outside his restaurant, allegedly by Al Capone.
August – In a daring daylight robbery, Timothy D. "Big Tim" Murphy and his gang rob a mail train of $400,000 ($5.2 million today). Murphy is indicted in February 1921, and convicted in November 1922.