The Mafia families took advantage of Prohibition to make fortunes.
Frequently they fought each other for control of cities.
In New York, the Castellammarese War gave organised crime figure, Salvatore Maranzano dominance. He became “the boss of bosses” and established a Mafia Code of conduct, which was binding on all members.
There were gangsters in every city.
In Chicago, Dion O'Bannion controlled the bootleg business in the south of the city and John Torrio in the north. The mayor of Chicago, 'Big Bill' Thompson, was under the influence of John Torrio.
One of the most notorious gangsters was Al “Scarface” Capone.
He ran massive bootlegging, prostitution and gambling rackets in Chicago, in the late 1920s.
He dominated a range of ethnic gangs, for example the Italians, Irish, Jews and black Americans.
He controlled city officials, like judges, through bribery or intimidation. During elections, he stationed gunmen on the roofs of polling stations to ensure officials on his payroll were elected.
The most notorious events associated with Capone were “The St Valentine's Day Massacre” 1929, when he ordered the murder of seven of his main rivals, and “The Last Supper” 1929, when he personally battered three Sicilians with a baseball bat.
An elite group incorruptible Prohibition Agents, known as The Untouchables and led by Eliot Ness, was assigned to bring Capone’s bootlegging to an end. While they were raiding Capone’s distilleries and warehouses, Frank Wilson of the Inland Revenue Service (IRS) investigated his finances for income tax fraud.
In 1931 Capone was finally arrested not on murder or racketeering but on tax evasion, and successfully prosecuted.
He was initially imprisoned in Atlanta, Georgia, but transferred to the “escape-proof” Alcatraz Island in 1934.
After the ending of Prohibition organised crime was less visible, but it remained powerful. J Edgar Hoover and the FBI developed forensic laboratories in 1932 to help convict criminals but success was limited.