I note that the Big List now contains entries for the names of all the states as well as some Canadian provinces. Very interesting. I expect you’ll get around to the rest of Canada, plus the name Canada itself, in due course.
I wish to note one minor error in the entry for Washington. It says that Washington Territory initially extended to the land now owned by Oregon. Not true. See this wiki page on Washington Territory for details.
Just a suggestion (which you may ignore if you wish), but you might mention in the entry for Oregon that there’ve been numerous suggested etymologies for that name. Almost as many as there’ve been for “OK” or “the whole nine yards”. Well, maybe not that many, but quite a few. George Stewart lists about a dozen or so in his book Names on the Land.