(Feb. 14, 1929), mass murder of a group of unarmed bootlegging gang members in Chicago. The bloody incident dramatized the intense rivalry for control of the illegal liquor traffic during the Prohibition Era in the United States. Disguising themselves as policemen, members of the Al Capone gang entered a garage at 2122 North Clark Street run by members of the George “Bugs” Moran gang, lined their opponents up against a wall, and shot them in cold blood. The victims included gang members Adam Heyer, Frank Gusenberg, Pete Gusenberg, John May, Al Weinshank, and James Clark, as well as a visitor, Dr. Reinhardt H. Schwimmer.

The St. Valentine's Day Massacre and other gangland killings, frequently portrayed vividly by the mass media throughout the world, came to symbolize the violence of the Prohibition Era in Chicago.