Re: Full Spring Road Trip
Well, you're certainly the envy of pretty much everybody on these boards. Rather than classify anything as a "must see", I'll suggest some "must consider"s. What you MUST see is up to you.
NY -> Miami: The Blue Ridge Parkway, absolutely the most scenic way to get from DC to Ashville, NC
Miami -> San Diego: All the high spots have been noted
San Diego -> Seattle: The coast highway (CA-1) for sure, Monterey/Carmel, the Oregon Coast
Yellowstone -> S. Utah: Dinosaur National Park (the west entrance from Vernal, UT)
S. Utah -> LA: Scotty's Castle in Death Valley National Park, tour a brothel (they're legal in some counties in Nevada, and some do give free tours)
LA -> Chicago: Meteor Crater, Petrified Forest National Park, St. Louis (zoo, arch, river boat tours)
Chicago -> Detroit: Not much to recommend on this segment
Detroit -> Montreal: via Canada to Niagra Falls, via USA through Thousand Islands to Ottawa (Canada's capital)
Montreal -> NY: Franconia Notch & Kankamagus Highway in Northern NH, drive to the top of Mt. Washington; Cape Neddick Lighthouse (the Nubble) in York, ME; Boton Heritage Trail
Seeing these and the other suggestions you've gotten here, you'll have covered more of the best of America than most natives.