Yeah, that's what I thought. Although I did know there's a great deal of controversy over how far east if goes, and people laugh at New Yorkers for thinking of Cleveland as basically the same as Kansas.

In Canada, the Prairies go from the Rockies to the Shield region where things get stony and boggy. And extend north until it's too forested for the descriptor to apply, maybe a quarter of the way to the Arctic coast on average (so it's mostly taiga nd tundra with just a little bit of farmable area).

In the US, the "Midwest" means the area from Ohio to the Dakotas (and with a southern limit along the Ohio river and southern border of Missouri and Kansas).

Montana is full-blown "West" (or sometimes "Mountain West" or a member of the "Mountain States," if you want to distinguish it from the "West Coast" or "Pacific Northwest.")

I've never seen or heard Montana called Midwest. It's more Rockies or Northwest. Eastern half could be considered Great Plains-ish.