Organized crime, particularly in the US as a result of the 18th Amendment (Prohibition) in 1919.
Bootlegging activities (importing or making illegal liquor) and speakeasies (where alcohol could be illegally purchased) gave rise to rivalry that resulted in hired gangs of criminals (gangsters) and gun battles. One of the most notorious gangsters was Al Capone.
The law was difficult to enforce; illicit liquor could be brought into the US over the long land borders or coastline, and illegal distilleries were soon established. Social unrest and a widening gap between rich and poor also created a climate in which crime flourished. In 1933 the 21st Amendment was passed, repealing Prohibition. This, and the actions of the Federal Bureau of Investigation under J Edgar Hoover, limited the opportunities for the gangster and contributed to some reduction in crime.
Engaging in a racket.