With the Vegas skim, it's arguable that the Outfit was the most powerful mafia family in the 1970's. I'd imagine another time the Outfit was arguably the most powerful mob family was in the 1930s. There's a reason Lucky and the guys in NY allowed Chicago on the commission, and if you read a lot of Mario Puzo, it's probably not because they liked Chicago...

"...the successful annihilation of organized crime's subculture in America would rock the 'legitimate' world's foundation, which would ultimately force fundamental social changes and redistributions of wealth and power in this country. Meyer Lansky's dream was to bond the two worlds together so that one could not survive without the other." - Dan E. Moldea