Originally Posted by BFlinn181
I'd travel I-68 to I-79 and I-64 to St. Louis. Lots of things could stop and explore along the way. From St. Louis, you could go I-70 to Denver and the Rockies, then south through Utah to Arizona. Or at St. Louis continue SW on I-44 to I-40 and on to Arizona. Many National Parks and monuments on either route. Use Google to explore each route and pick things you'd like to take side trips to visit.
+1. You could take one route out and the other back. I've done them both, I-70 and I-40, although the latter was thirty years ago. There's so much to see and do that you'll never see it all, and rather than get frustrated by lack of time, I'd pick a few MUST-SEEs and plan around that, with a bit of wriggle room if you need it. Granted, the upper panhandle of Texas, Oklahoma and Kansas are not as scenically gifted as the Rockies or the Canyon, so if it's landscape you like, you can buzz through the middle parts there and spend more time in the west. Not putting down Kansas or Oklahoma City, but for certain things, you just can't beat Glenwood Canyon on I-70, or the Petrified Forest on I-40, Flagstaff, the North Rim, Arches, etc etc.
In any case, have fun and enjoy!