PBS
Pbs: American Experience: Public Enemy #1: Gangsters During the Depression
"Gangsters" in the Great Depression were divided into two different groups: Mobsters and Outlaws. This article discusses the differences between the two and the role each group played.
Chicago History Museum
Encyclopedia of Chicago: Gang Map
A map of the gang territories during the 1920s in Chicago. Shows where each of the gangs had a dominant presence.
Other
University at Albany: Organized Crime and Prohibition
Features statistics and details about organized crime and prohibition including facts on some of the more colorful gangsters during that era.
Other
Roaring 20s Gangster Links
Provides a list of links regarding the 1920s most famous gangsters, bootleggers, rumrunners, drug peddlers, and labor racketeers.
Other
Mystery Net: st.valentine's Day Massacre
The story behind the St. Valentine's Day Massacre. While gangland warfare was commonplace in Chicago during Prohibition, this attack was unusual because all of the victims were known mobsters.
Siteseen
Siteseen: American Historama: St. Valentine's Day Massacre
A comprehensive overview and a list of interesting facts pertaining to the St. Valentine's Day Massacre which made Al Capone and his Chicago Mafia national celebrities.
Siteseen
Siteseen: American Historama: Chicago Mafia
A comprehensive overview with many interesting facts and information on the Chicago Mafia who were part of the organized crime wave led by Al Capone during the Prohibition Era.