He rose from the slums of Brooklyn to take on the biggest Mafia dons of the 1950s and 1960s. Joey Gallo began his criminal career as a small-time loan shark.

In the 1970s, a group of ruthless Irish punks called the "Westies" managed to terrorize Hell's Kitchen in New York City.

Notorious heroin kingpin Leroy "Nicky" Barnes went from organizing one of the most powerful African American heroin rings in New York to a government informant.

He came to the U.S. from Italy in 1893, when he was seven years old. The Nitti family settled in Brooklyn, but by 1920, Frank had moved to Chicago.

This mobster rose from a foot soldier in Al Capone's Chicago "Outfit" to eventual boss of the notorious gang.

From the Castellammarese War in the late 1920's to the assassination of the Boss of Bosses, Paul Castellano, this episode explores six of the most notorious mafia killings of all time and the effects these murders had on organized crime.