What are the “Must-see” Parts of America on a cross-country drive?
Let’s say, Philadelphia to San Francisco or Los Angeles.
There’s always the world’s largest ball of twine in Cawker City, KS.
The red rock mountains in Sedona, AZ… Breathtaking.
Skip TX altogether but do get down to the FL Keys.
The best things are in the southern Utah/northern Arizona area. Of course the Grand Canyon, but also Bryce, Zion, Capital Reef, Arches and Canyonlands National Parks. Plus Monument Valley, the Painted Desert and several Cliff Dweller ruins. It’s my favorite part of the country.
A bit of a detour, though.
The drive down 89 through Utah into Arizona is one of the most beautiful that I’ve seen. You pass within easy read of Zion, Bryce Canyon, the Grand Canyon, Flagstaff and Sedona. It’s all amazing if you’ve never been out west before.
ETA: What Panache said…
If you take a very Southern route, New Orleans is a must see and do.
Niagara Falls is a must see.
I assume that you will buying a new Family Truckster for this trip right?
And Canyon de Chelly! MUST DO CANYON DE CHELLY!
Yep, and Mesa Verde, in the SW corner of Colorado.
And my favorite place: Horseshoe Canyon.
Shut up, Shut up, Shut up, Shut up, Shut up 
MONUMENT VALLEY is wonderful and you’ll go right by it on you way to Canyon De Chelly.
Also, if you’re going down I-80, stop at Ole’s Big Game Bar in Paxton NE it’s the only thing interesting until you get to the Rockies
One of the few extremely interesting things in Iowa is the Amana Colonies. The Amanans were one of the communitarian religous groups that came to the U.S. in the late 1800s, somewhat akin to the Shakers. Although the communal lifestyle is gone, the town remains a profit-sharing community (manufacturing textiles, furniture, cuckoo clocks and strudel) , with a small museum about the history of the community which is fascinating. And all the family-style German food you can stuff your face with.
Everyone seems to be neglecting the East.
A lot depends on the amount of time you have. Much also depends on your interests. Scenery? Cities? History? Geology? Night life? Museums or just wave as you pass?
From Philly, there are beautiful mountain views all through Pennsylvania. West of Pittsburgh you can choose I-80 up toward Cleveland and Chicago or I-70 through Columbus and Indianapolis. I’m not a huge fan of Columbus, but the other cities all have something to recommend them. You can also jog down I-71 from Columbus to Cincinnati and Louisville, following the Ohio River. Chicago has lots to recommend it, but even Cleveland has a view of a Great Lake. The central path is only so-so, but the Southern path passes through really pretty areas of Kentucky, Indiana, and Illinois. (The southern sections of the latter states are filled with beautiful hills, very different from the billiard table that extends across the central and northern regions.)
If you take the southern route, but only if you have a bit of time, you might want to get off the freeway before Cincinnati and visit Serpent Mound way off the beaten path in Southern Ohio. (About 10 miles Southeast of Hillsboro on S.R. 73, nearly 40 miles East of Cincinnati.)
Regardless which of those routes you take, you do want to aim for St. Louis with its history. If you have gone to Louisville, you need to take I-64 toward St. Louis. A side trip to Vincennes, IN, is both pretty and historic. East of St. Louis, just off I-70 (and I-55 from Chicago), are the Cahokia Mounds. (They are also only 2 1/2 miles from I-64.)
From St. Louis, you can either follow I-70 West to Denver or take I-44 Southwest, then I-40 West, following (roughly) the old U.S. 66 path. It goes through the Texas Panhandle which gives you an opportunity to detour South, (not really that far), across the Llano Estacado to Palo Duro Canyon, then continues on to New Mexico and Arizona near the Four Corners region about which everyone before me has been gushing.
If it weren’t for the weather, I think Chicago would be one of the best destinations in the US. By the lake, great food, great theater, cool music clubs, nice people…a really fun place to go (in the spring or fall).
Otherwise, be sure to stop by Las Vegas!
BTW, What the deuce?, I see from another thread you started that you are taking this trip for the first time. If you are from a foreign country, you do know that this is one hell of a schlep?
I say that as I lived in Germany and had a guy tell me he intended to drive from NYC to Los Angeles, in a week, in December, and wanted to know what to see along the way. I had to explain this was going to be anything but a leisurely trip and he would be lucky to get there in that amount of time, let alone stop along the way and do “touristy” things.
I’m American. I have heard comments from foreigners about how huge the United States is (though presumably Russians wouldn’t make such a comment 
).
I have a window of 10 days to do this trip, but I won’t have too many opportunities like this. If the logistics look too bad, I’ll probably just fly to California, and drive around that one state for a week, then fly back. There should be enough to see in San Fran/LA/San Diego to occupy a week, especially if I also drive to Seattle.
Now I’m confused. You’re thinking of doing a *round trip *in 10 days? And your alternate plan is to drive through SF, LA, SD, and Seattle in a week???
If this is the case, you’re being more than a wee bit optimistic.