Just a theory:
Those of us who went to elementary school in the late 80's and on tended to play a lot of Oregon Trail. In fact, if you didn't grow up here, that was probably your entire frame of reference where Oregon was concerned for many years.
I'm starting to wonder if that game might have delivered subliminal messages to those generations of children, since the rapid influx of transplants in the last decade or two has mostly been people within that age range.
Unfortunately it's a lot harder to die or dysentery these days, so there's getting to be a LOT of us.