The major Mafia centers in the US, in addition to NYC, were Chicago, Boston, Philadelphia, Kansas City, Buffalo and Los Angeles. Often the family in one of those major cities operated adjuncts in other cities, for example, Chicago=Dallas and Buffalo=Toronto. Several families had a presence, but not an overpowering presence, in Vegas ( Mafia nfluence in Vegas has been vastly exaggerated). I put this in the past tense because, with the overall drastic weakening of the Mafia, there's really no telling who's in charge in some cities and outposts anymore.
Mick, please note that US Mafia has always admitted non-Sicilian Italians to full membership. And plenty of Dons weren't Sicilian.
You may be thinking of the Chicago "Outfit" under Torrio and Capone, which was never a Mafia family.