Is there some reason that would continue to be true if Southern California[1] was replaced with swamps?

[1] You're using "Northern California" and "Southern California" differently from everyone else; in normal use, Northern California is the Bay Area, not the north of the state.

> You're using "Northern California" and "Southern California" differently from everyone else; in normal use, Northern California is the Bay Area, not the north of the state.

No, norcal is north of LA, not just the bay area. I’ve never heard of anybody referring to the bay area as norcal, it’s always “bay area”

I mean, I assume there's a vaguely-defined line between San Francisco and Los Angeles that notionally separates the north from the south. It doesn't make any more sense to say Southern California is nothing but LA than it does to say Northern California is nothing but the Bay Area.

But my point is that the region to the north of, say, Berkeley, is not part of "Northern California". It's too far north for that.

I’m from Sierra County, is that north enough for you?

We consider ourselves part of Northern California and have since at least the 70s. For many up there, the Bay Area is only nominally part of Northern California, in fact as a kid I didn’t think it was. But having gone on to live in San Francisco for a long time, I came to realize that the the Bay Area, for better or for worse, has more in common with Redding then it does with Manhattan Beach.

But I can’t figure out what you think the too-northern Northern Californians should call themselves if they let you lop off the Bay Area (and most would thank you for it).

https://en.wikipedia.org/wiki/Northern_California