Welcome, Larry, and thanks. The historical context is wonderful.
The closest equivalent in Alaska to Flatlander must be Cheechako. Originally a Chinook Jargon term meaning, essentially, newcomer or non-native person, it seems to have transferred to English as meaning greenhorn or tenderfoot, thus still newcomer, but is pejorative to a greater or lesser extent depending on the speaker, the circumstance, and the era. Most recently it seems to have been used with a mixture of disdain and humor, sometimes with a touch of showing off, usually used by someone who hasn't been here all that long to refer to someone who's been here even less time. I haven't heard the word much in the past twenty years or so, so my unscientific belief is that it's in decline.
While I'm not quite alone, my liberal vote makes scarcely a ripple in this conservative state. I can't imagine ever leaving.