I was just looking at this thread, came across my reply from six months ago, and remembered another museum worth checking out: The Owls Head Transportation Museum in Owls Head, ME. I've visited a couple of times while in ME visiting family, but didn't make it the last time I was up there in 2017.
From the website: OHTM is a nonprofit educational organization. Its mission is to collect, preserve, exhibit and operate pre-1940 aircraft, ground vehicles, engines and related technologies significant to the evolution of transportation for the purpose of education.