Sicily is the estereotype for the Italian mafia since a
notorious family was originated in Sicily.
^
wrong
The area in which ALL Italian Mafia are based is the Italina
island of Sicily, the capital of Palermo being the hub of its
activities. different areas of Italy have different criminal
organisations, but none are as successful or notorious as the
Mafia.
However, I assume you are talking about the American Mafia. In
its origins, all members of the American Mafia were from Sicily or
descendants of Sicilians. However over the years, as the
descendants of Sicians have bred with the descendants of mainland
Italians, and as a result the American Mafia's members are made up
of a mixture of Sicilians and mainland Italians.
Although they are unconfirmed, there is even reports nowadays
that the American Mafia is inducting people whom are only half
Italians