Miscellaneous: North Dakota License Plate Finally Spotted

Yesterday I spotted a car near Santa Rosa, CA bearing a North Dakota license plate. That's not a big deal, except in the context of a game I've been playing with myself for about three years now. I've been trying to see a license plate from each of the 50 United States--without going out of my way to do that. I had been stuck at 48 states for well over a year.

North Dakota was one of the two I'd never seen (oddly, South Dakota is moderately common around here; I've seen South Dakota plates a handful of times). Logically, Hawaii and Alaska would seem the most unlikely in Northern California, but I see Alaska plates once or twice a month and Hawaii not infrequently either. In addition to the 49 states I've now seen, I've seen plates from Washington D.C. and even the Marshall Islands--all in the course of my regular wanderings around the San Francisco Bay Area. One state still eludes me.... Care to guess which one it is, or what the other rare ones seem to be?