I was fortunate to travel along route 66 multiple times from Los Angeles. Once all the way to Chicago. The thing that is most embedded in my mind from those trips - The Burma Shave signs all along the route. It was fun for us as children whenever one came along. We also played license plate baseball from time to time.
Anyway, I was bitten by the road-trip bug at a very early age and have seen many fascinating and wonderous things in my travels. Not knowing the routes you intend to take, the suggestions I am about to offer may be well off your path, but it is fun to share my travel experiences and what follows is presented in a rather scattershot manner.
Each state has something remarkable in it worth visiting, from natural wonders to man made structures.
I cannot possibly list everywhere I have been in the U.S or this could be overwhelming. Here is a picture of one of the great natural wonders in the state of Idaho.
That is a picture of Shoshone falls, higher than the Niagara falls. It is actually a collection of descending cascades. Situated on the Snake river, I was fortunate to snap this photo and many others when it was at full flow. I was fortunate as the flow gets diverted to produce power most of the time, but it is still worth a visit in my estimation. Also in Idaho is Craters of the Moon.
I have been to Devils Tower in Wyoming which has a nearby Prairie Dog Town. Also worth a visit in that state is Fort Laramie.
It is a vast site with the core consisting of many restored structures, but there are many outlying ruins of once large buildings. There are other places to see in Wyoming as well.
If you are into volcanoes, their are many in the northern part of the Pacific coast: Mt Lassen, Mt. St. Helen's
, etc...
Then there is the Columbia River Gorge with some spectacular scenery and this odd bit of a monument on the Columbia River in Washington State across from Portland.
It is a replica of Stonehenge as it might have been and built as a war memorial.
Utah has a great many natural wonders, but they are overrun with tourists over the warm weather moths and can be a bit of a nightmare to visit. Moab is a gateway to the Colorado river as well as other interesting places but it too has become a bit crowded in the spring and summer months.
I love caves and in 1983 did a walking tour of Mammoth Cave in Kentucky and a little less than 48 hours later a walking tour of Carlsbad Caverns in New Mexico (Hey I was 38 then: more active and a little crazy to do that). Then you did not need a reservation to take a tour, but now it is probably advisable.
I will stop now before I bore everyone even though I have not covered a tenth of everywhere I have roamed.. I love travel by automobile wherever I visit. The ability to just go where serendipity takes you leads to wonderful discoveries. Too much rigid planning on a trip can rob one of those, but I understand the need for a starting Itinerary.
Wherever you wander, may you also enjoy your road trip.
(All attached photos are from my personal history)