Obama almost winning here in 2008 was something.
I mean Clinton won it in 1992, so its not ancient history. North and South Dakota being competitive in that election honestly seems far more quirky with today's lens.
South Dakota was very close in 1992 as well. While we like to think of presidential elections as 51 individual contests, the reality is there are usually trends that persist across the map. The Dakotas are pretty similar to Montana ideologically, so it makes sense that if one is close, the other will be too.