According to Peter Maas`s book "Underboss", Sammy Gravano was made by Paul Castellano, who was the boss between 1976 and 1985. So 1957...

However, Mafia needs more members, if the books remain close "forever" there would not be boss, caporegime, soldiers to promote, there would be only associates and you cannot put an associate as a Boss. In my opinion, I could be wrong. Unless Mafia rules has changed and we didn`t know! jajaja