Born in Brooklyn, New York, in 1899, of an immigrant family, Al Capone quit school after the sixth grade and associated with a notorious street gang, becoming accepted as a member. Johnny Torrio was the street gang leader and among the other members was Lucky Luciano, who would later attain his own notoriety.
About 1920, at Torrio's invitation, Capone joined Torrio in Chicago where he had become an influential lieutenant in the Colosimo mob. The rackets spawned by enactment of the Prohibition Amendment, illegal brewing, distilling and distribution of beer and liquor, were viewed as "growth industries." Torrio, abetted by Al Capone, intended to take full advantage of opportunities. The mobs also developed interests in legitimate businesses, in the cleaning and dyeing field, and cultivated influence with receptive public officials, labor unions and employees' associations.
Torrio soon succeeded to full leadership of the gang with the violent demise of Big Jim Colosimo, and Capone gained experience and expertise as his strong right arm.
In 1925, Capone became boss when Torrio, seriously wounded in an assassination attempt, surrendered control and retired to Brooklyn. Capone had built a fearsome reputation in the ruthless gang rivalries of the period, struggling to acquire and retain "racketeering rights" to several areas of Chicago. That reputation grew as rival gangs were eliminated or nullified, and the suburb of Cicero became, in effect, a fiefdom of the Capone mob.
Perhaps the St. Valentine's Day Massacre on February 14, 1929, might be regarded as the culminating violence of the Chicago gang era, as seven members or associates of the "Bugs" Moran mob were machine-gunned against a garage wall by rivals posing as police. The massacre was generally ascribed to the Capone mob, although Al himself was then in Florida.
The investigative jurisdiction of the Bureau of Investigation during the 1920s and early 1930s was more limited than it is now, and the gang warfare and depredations of the period were not within the Bureau's investigative authority.
The Bureau's investigation of Al Capone arose from his reluctance to appear before a Federal Grand Jury on March 12, 1929, in response to a subpoena. On March 11, his lawyers formally filed for postponement of his appearance, submitting a physician's affidavit dated March 5, which attested that Capone, in Miami, had been suffering from bronchial pneumonia, had been confined to bed from January 13 to February 23, and that it would be dangerous to Capone's health to travel to Chicago. His appearance date before the grand jury was re-set for March 20.