[Docere]

It's interesting that San Francisco really doesn't have any Italian or "white ethnic" neighborhoods to speak of, even though it was (I believe) over 10% Italian at one time. Certainly when they suburbanized, they did not form new concentrations in the suburbs, they just melted in with other whites.

I believe the majority of SF Italians came from northern rather than southern Italy.

ETA: I don't know if North Beach is any more "authentic" than Manhattan's Little Italy, but it probably has more symbolic importance in some ways, since NYC has plenty of other, more authentic Italian areas.