How powerful were the mafia in the US? Why did they decline, and has anyone tried to restore or replace them?

by Artyomic
Artyomic

20th Century onwards; probably be better if I limited the question to the Northeast.

Actually, follow-up question: I've heard all about the organized crime in the West and NorthEast. I can't think of any Southern groups- what was organized crime in the South like?

koga90