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the beginning of what is known as the Gangster Era, a time that roughly spans from 1919 until 1933 when Prohibition was repealed.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
Prohibition also had an effect on the music industry in the United States, specifically with jazz. Speakeasies became very popular, and the Great Depression's migratory effects led to the dispersal of jazz music, from New Orleans going north through Chicago and to New York. This led to the development of different styles in different cities. Due to its popularity in speakeasies and the emergence of advanced recording technology, jazz's popularity skyrocketed. It was also at the forefront of the minimal integration efforts going on at the time, as it united mostly black musicians with mostly white audiences.