Tuesday Night Trivia

This may or may not become a recurring feature. At any rate, here's tonight's trivia challenge:

There are two pairs of states for which both states' two-letter postal abbreviations use the same two letters. Name them.

To clarify: If you add Canadian provinces to the mix, you end up with a third pair. I'll use this pair as an example—the two-letter postal abbreviations for Kansas (KS) and Saskatchewan (SK) use the same two letters. There are two more, entirely American, pairs. Those are the ones I'm looking for.

The first person to correctly answer the question may or may not win a prize of some sort. I'm leaning toward "may not," but I might come up with something.

Oh yeah, try to answer the question without looking up the abbreviations on Wikipedia, USPS.com, or some other reference site.