Maine by a pretty good margin. Peaceful, quiet, decent weather, not jammed pack with people, etc. Can't really think of anything negative to say about it.
I'd be a fan of living in Alaska if I weren't disabled; I just feel like its too rural/remote for the kinds of problems I have. If I were able bodied, though, it would likely be up there with Maine.
I wouldn't be keen on living in the South, not a fan of the climate down there, so Texas and Florida are out. Especially Florida with the humidity.
And I definitely wouldn't want to live in California or New York, for political reasons. Plus just too many people... I get there are plenty of rural options in those states, but even if I lived as rural and as far from the cities as possible, the cities would still dominate the state and I'd be forced to live according to fringe leftists whims, so no thanks.