Chicago
The ratification of the 18th amendment to the Constitution in 1919 made the production and sale (including exportation) of alcoholic beverages illegal in the United States. This ushered in the beginning of what is known as the Gangster Era, a time that roughly spans from 1919 until 1933 when Prohibition was repealed. The 1920s saw gangsters, including Al Capone, Dion O'Banion, Bugs Moran and Tony Accardo battle law enforcement and each other on the streets of Chicago during the Prohibition era. Chicago was the location of the infamous St. Valentine's Day Massacre in 1929, when Al Capone sent men to gun down members of a rival gang, North Side, led by Bugs Moran.
Prohibition in the United States
Mark H. Moore states that contrary to popular opinion, "violent crime did not increase dramatically during Prohibition" and that organized crime "existed before and after" Prohibition. Kenneth D. Rose, a professor of history at California State University, maintains that the idea of a "prohibition crime wave was rooted in the impressionistic rather than the factual."