Merriam defines it generically as:
the chiefly northerly sections of a state
But in their examples, every single one can be traced back to New York. For example:
By 2017, Lopez, after earning her GED and briefly attending college upstate, was living with an aunt in Brooklyn.
If I'm in, say, Duluth, is that "Upstate Minnesota"?
In more general terms --
Did the phrase come about just because Not New York City needed to be differentiated from New York City?
Does the phenomenon apply anywhere else?
For example, almost all of the humans in Nebraska live in the Omaha-Lincoln metro on the extreme eastern side of the state. There are something like eight hours of driving west to Colorado without much in it. I think they refer to that area as "Western Nebraska," which means, essentially, "Not Omaha Or Lincoln."
Is there some name for this "exclusionary reference"?