Atlantic City

From The Godfather Wiki

A city in New Jersey, Atlantic City was renowned for it's gambling, a trait that made Vincent Mancini a frequent visitor.

It was in Atlantic City that Michael Corleone called a meeting with the Commission, where he returned all of their shares in his casino. Shortly after, the Commmission was wiped out by Joey Zasa, leaving only Michael, Don Altobello and a few other dons alive.