Plymouth village, Mayflower II.
Cape Cod.
Acadia National Park in Maine... we stayed at Blackwoods campground, no hookups, loved every minute of it. Been there twice (so far!), planning on going a bunch more times.
Washington DC to do the "Nations Capitol" thing... the big thing I regret that we didn't get to when our kids were younger. I still want to do it, but with the kids just hitting 20 years old I doubt they will be with us.
Niagara Falls. We stayed on the Canadian side. Great adventure, had a wonderful time. In one sense a disappointment due to the tourist trap aspect of the area, but worth visiting (once, at least).
Gettysburg Battlefield in Pennsylvania.
When you really start looking, there is just an amazing amount to do and see.
Actually, just in Connecticut there are dozens of campgrounds, big and small, to check out. The last couple years we've been staying at mostly the no-hookups state parks - every year it seems I find another one I didn't know about, almost all within an hours drive. Amazing what is right near us, sometimes you just have to make an effort to look harder!
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2021 F150 2.7
2004 21' Forest River Surveyor