Originally Posted by syencer
The redwoods in California, Yosemite, Mt. Rushmore just for a few!!
Unfortunately, those sites are nowhere near where the OP is going.
If you are going to Carlsbad, you are most likely going to see the caverns, and they are worth it.
The Meteor Crater in Arizona is pretty cool.
If you get as far as Kingman, AZ, the drive up to Oatman is a nice day trip. Just don't take your camper, as its kindof windy.
On the way back, if you wander into soutwest Colorado, there is a steam engine train that goes from Durango to Silverton. Absolutely awesome.
And if you want to camp in Silverton, you can rent a jeep and cruise the old mining roads, stunning scenery.
There is obviously far more than can be packed into just three weeks!
Have a great trip.