The Saint Valentine's Day Massacre is the name given to the 1929 murders in Chicago of seven mob associates of North side gang leader Bugs Moran. The men were all gunned down on February 14th of that year--hence the popular name of this infamous event.
The horrific bloodbath was the result of a struggle between Moran and South sider Al Capone to take control of organized crime in Chicago. It is widely assumed that the Massacre was an attempt orchestrated by Capone to kill Moran. One of Moran’s associates, however, was similar in height and body shape to his boss, and was even dressed much like Moran normally dressed that morning. Capone’s “spotter” for the crime is believed to have mistook the associate (Albert Weinshank) for Moran, who was a late arrival to the meeting that brought his associates together. Moran and three gang members who also arrived late thus narrowly avoided being gunned down that morning.
There is a St. Louis connection to this infamous event. Several former members of the Egan's Rats gang were also suspected of having played significant roles in the Massacre while working for Capone.
Wikipedia article—Saint Valentine’s Day Massacre:
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Foreword by Estes Kefauver.
Author/Compiler: Peterson, Virgil Wallace.
Local Call Number: ST--364.977
Publication Date: 1952.
Title: Chicago's unsolved crimes & mysteries.
Author/Compiler: Alaspa, Bryan.
Local Call Number: WA--364.109773
Publication Date: 2013.
Title: Deadly valentines: the story of Capone's henchman "Machine Gun" Jack McGurn and Louise Rolfe, his blonde alibi.
Author/Compiler: Gusfield, Jeffrey.
Local Call Number: SS,BU,CP,DA--364.10922
Publication Date: 2012.
Title: The dry and lawless years.
Author/Compiler: Lyle, John H.
Local Call Number: ST--364
Publication Date: 1960.
Title: Encyclopedia of organized crime in the United States: from Capone's Chicago to the new urban underworld.
Author/Compiler: Kelly, Robert J.
Local Call Number: SS,BA,BU,CB,CP,DA,SC--364.1060973
Publication Date: 2000.
Title: Get Capone: the secret plot that captured America's most wanted gangster.
Author/Compiler: Eig, Jonathan.
Local Call Number: BU,CP,DI--B CAPONE AL
Publication Date: 2010.
Title: The man who got away: the Bugs Moran story.
Author/Compiler: Keefe, Rose.
Local Call Number: SS--364.1066092
Publication Date: 2005.
Title: The St. Valentine's Day massacre: the untold story of the gangland bloodbath that brought down Al Capone.
Author/Compiler: Helmer, William J., & Arthur J. Bilek.
Local Call Number: CO--364.1523
Publication Date: 2004.