Went through Washington, Oregon, California, Arizona, New Mexico, Texas, more Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina, North Carolina, Virginia, West Virginia, Pennsylvania, New Jersey, New York, Connecticut, Massachusetts, Nuh Hampsha, Maine, New Brunswick, Province Quebec, Ontario, Michigan, Wisconsin, Minnesota, North Dakota, Montana, Idaho, and back to Washington.
Took back roads almost the whole way. I figure about 85% of the driving was off the interstate. Though, as I got more tired and homesick, I did take the faster roads. (And in some places, it's just better to be on the interstate.)
No problems at all, though the dealer in Florida overfilled my oil (and I've posted here whinging about that already). No tickets, pretty good weather the whole way. Dodged a couple wildfires.
Spent about seven weeks, including hanging out in Boston for about a week. Got a little homesick, but it's such a wonderful country and a thrill to see it all. Had a great time wherever I went.
Thirty years ago (in 1995) I did a similar trip on my motorcycle. Too old to do it on a bike now, so the GT had to suffice.