I am writing a book based on the NYC Mafia families and it got me interested in the topic. During which time period where the NYC mafia families at their peak of power and what did they do for money/success?
This happens to be an incredibly busy week for me, so I simply don't have the time right now to give you a long, detailed answer up to the standards of /r/AskHistorians. That said, I have a huge library of New York City history books so I can give you some good recommendations for further research:
I hope those recommendations point you in the right direction. I am sorry I couldn't be more help; if I can find some time later on, I'll try to answer your question properly.
I'd like to see an answer to this too. Paging /u/discovering_NYC, newly flaired specialist on NYC history!