Skipping the big ticket items that will be obvious such as the Grand Canyon and Yellowstone, I'll suggest instead a few that I've hit over the years that most people would overlook. Just west of Hagerstown MD where I-70 and I-81 hook up, there's a town called Big Pool with two quietly intriguing places, Fort Frederick State Park and the Chesapeake and Ohio Canal National Historical Park. Outside of Austin TX, there's a BBQ joint known as the Salt Lick. It's a local legend and worth the effort to find. In New Mexico, it looks like you'll pass near to Socorro. If so, it would be a shame to miss the Very Large Array which you'll recognize from any number of science fiction movies. And if that intrigues you, then while in Flagstaff AZ visit the Lowell Observatory where Pluto was discovered. Another little known venue in that same area is Walnut Canyon National Monument. As a side note, when I was last there, there were perhaps a dozen 'vettes in the parking lot. And be sure to use AZ-89A down through Oak Creek Canyon between Flagstaff and Sedona on your way to Phoenix rather than I-17. If you're going to stay north through Washington and northern Idaho, then consider US-12, the Lewis and Clark route, over Lolo Pass through the Rockies. But I'd also suggest that you consider a slightly more southern route, up the Columbia River Gorge and the Snake River Canyon with a particular stop at Bruneau Canyon and Bruneau Sand Dunes. And if you're a baseball fan, first my sympathies on Les Expos and second, the Field of Dreams is in Dyersville IA. Finally, I don't know why you're jogging to Milwaukee, but while there be sure to check out the harbor and art museum.
AZBuck