Frank (Salvatore) and Ralph Capone - Al’s brothers who infiltrated the Cicero government and police department
Johnny Torrio - Chicago mobster and Capone’s mentor
Frankie Yale - Mobster, gave Capone his first job at the Harvard Inn, Coney Island. Eventually murdered by Capone
Billy McSwiggin "the hanging prosecutor" - mistakenly shot and killed by Capone’s henchmen
Bugs Moran - Rival mobster to Capone and intended victim during St Valentine’s Day massacre
Elmer Irey - Officer at Special Intelligence Unit of the IRS, investigated Capone’s activities
Eliot Ness - Agent with the US Treasury Department's Prohibition Bureau, responsible for bringing Capone to book