James Joseph "Whitey" Bulger is the most infamous Irish American mob boss in American history and second on the FBI's Most Wanted List behind Osama bin Laden. He took over the Winter Hill gang in South Boston, Massachusetts after being released from prison in the 1960s. He killed 19 people.
Unlike anything the Italians could achieve, Bulger actually had a mole within the FBI. Corrupt agent John Connolly, also an Irish American, constantly tipped Bulger off about police and FBI bugs, wiretaps and other important information. His younger brother Billy was President of the Massachusetts State Senate.
Tipped one last time in 1995, Bulger went into hiding with his girlfriend Catherine Grieg. He spent 16 years on the run until he was caught in 2011.