Looks like it was in Colorado
http://www.summitdaily.com/news/colorado-parks-and-wildlife-lowers-bag-limit-for-arctic-char-caught-in-dillon-reservoir/
I could be wrong, but I think the referenced article refers to true Arctic char which get much bigger then blueback/ sunapee trout. I think blueback's are a subspecies or cousin of the char. Maine has the only native populations left, and I believe Idaho has a lake or two in which they were stocked a long time ago through F&G exchange, and they have taken to the lake and reproduce on their own now.
NH is rumored to still have some relic populations in a few spots, but their most likely just rumors (and you can't fish the lakes anyways). NH did have a population which grew to reportedly huge size in sunnapee lake, but it is now believed the very large specimens where hybrids which mixed with lake trout the state stocked. They cannot compete with other fish species from what I understand, and the population that was in sunappe lake was only discovered after the state stocked lake trout.
It is abucket list fish for me. More as a reason to see that area of Maine. I have never been much past Ellsworth, but it looks and sounds like a beautiful area.