Highway 15 thru Pennsylvania, NY, VA, WV, etc is a good fall roundtrip with farmer's stands fall colors bnb etc. + Gettysburg and Landcaster
Civil War Roundtrip thru MI, GA, TN, etc.
Old coastal southern cities - Myrtle Beach, Charleston, Savannah, Wilmington NC,
New England - Boston, Ivy Campuses, Newport RI, and the mountains
Midwest - Chicago, Cincinnati, MKE, Toldeo, Columbus etc.
The Pacific Coast roadtrip Seattle, Portland and if you are ambitious Bampf and Jasper