<-- driven / been in every state in the US EXCEPT: Hawaii, California, Maine, Vermont, New Hampshire, Rhode Island, Connecticut, Massachusetts (New England).
Otherwise I have seen every tourist trap, and little town it seems...
Top 5 places personally in no order:
Yellowstone, WY: Never went more than 1 mile off the parking lot, but rivers and waterfalls that were amazing and so pristine you could drink from them. Fed the prairie dogs from my hand at old faithful, they were cute
The sulfur from the hot springs was NASTY! but amazing to see, colors you have never seen and beautiful (hell I was 13 and I was in awe).
Grand Canyon, AZ: Wow!, I begged and begged to take the donkey ride down into the canyon, but no time. It's 100 times as big as any picture you have ever seen in a movie or from a postcard.
Mammoth Cave, KY: If you can spare the time, are in good physical shape TAKE the 4 hour tour! Even on the 2 hour you won't believe the beauty and amazing things you see (pro tip: even in 100º Kentucky heat wear jeans and a sweatshirt. It's always 55º down in there, don't be a tough guy you will be shivering BAD when you leave).
St. Louis Arch, MO: Kind of hokey but it is bigger than you think, my one regret is the TWO times I have passed it I never went up it.
Washington, DC: What can I say? There are way tooooo many things to see and go ooh ahh! You could spend 2 days alone at the National Air and Space Museum, another 3 seeing all that is there.
SIDE NOTES: Mt. Rushmore, cool for about 30 minutes then you realize you are a mile away from something amazing and you can't get near it / touch it, and any picture you take has been done by 1,000,000 postcard manufacturers for years. Badlands National Park, just as cool as Petrified Forest National Park. Creepy desert land with odd stuff. Neither better than the other, hokey shops ensue.
My own choice? I'd take US40 the southern route. Through Las Vegas, see the strip, over Hoover Dam, Grand Canyon.from there it is a toss up.
Pretend you went north to Yellowstone. From there you have the Corn Palace, Custard's Last Stand then nothing but corn and cows for 1000 miles + until you get past Ohio. You can detour way north for Rushmore if you like but thats about it.
If you go south 40, you can cut up US25 through Colorado Springs (MUCH more scenic route with mountains and toejam, and if you like and go up Pikes Peak). From there corn and cows for 1000 miles (bad either way). BUT from St. Louis you can cut south on 64 and get through some of the south, see the cave, and see hill billys in their natural state, also the Appalachian Mountains, the little inbred cousins of the Rockies. From there up through DC and all I mentioned.
As a kid we did 4 "2 week" drive vacations. Stepfather's mother lived in Omaha, NB (Living in Milwaukee, WI so picture the route). One went across the north to Seattle, through Mt. Rushmore, the badlands, and back through Yellowstone, then Nebraska. Second through Nebraska to Colorado, then south through the Grand Canyon (missed Hoover Dam
) then back through Nebraska. Third south to New Orleans, then Florida to see a shuttle launch, then back through Memphis (Grand Old Opry, Ruby Falls, Mammoth Cave, all that). Fourth Went out to Seattle again, down through Salt Lake City and all we might have missed like the Corn Palace and Custard's Last Stand before).
I seen it all, and hope this helps plan your route. Have a TON of fun, eat at every mom and pop diner you can find, hit up AAA for travel guides and read through them before the trip, you'll find fun stuff.
Just to throw a monkey in the wrench, US HWY 50 headed east from you is beautiful and stuff, 50 to 93 to Salt Lake City, Looking at the route I may have been in CA for a few miles back in the day 395 south to Reno then over... might have to check that. Anyway you could go north or south from there, DON'T GO EAST. Nebraska is almost as bad as Montana nothing, nothing, nothing, nothing, nothing, did I say nothing?
