I am pretty sure that I have also run into some in North Dakota. These had been clearly planted deliberately, as landscaping, and were not where you would expect to find them (I was quite taken aback, actually, to see one!). Perhaps they were isolated far-enough from other biomes to make vectoring the disease impossible? I do know that one near where I grew up would try to grow every few years. It would make a good start, and then the blight would knock it back, seemingly killing it. This would happen again and again in my time there, even though there were no other Chestnut trees in the vicinity. I'm guessing the "blight" organism lives in the soils there?
