Here are a few......
1. Medicine Wheel/Medicine Mountain National Historic Landmark, located at 9640 feet on Bighorn National Forest.
2. Zion National Park
3. Bryce Canyon National Park (prettier than the Grand Canyon, by far)
4. If you are rolling through South Dakota, you might as well stop at Wall Drug.
5. Mt Rushmore and Crazy Horse monuments
6. Yellowstone National Park...I believe the government made entrance to the park free for veterans? It's worth seeing the Grand Canyon of the Yellowstone and fool tourists trying to get killed by grizzly bears for a picture. Jackson Hole isn't that far away and it has some cools shops (or at least it used to).
7. Lead, South Dakota. Located in the Black Hills, founded as a mining town (mosr productive gold mine in the West). Most of the town is preserved and is on the National Historic Register. If you like the old west and mining history, this would be fun.
8. Wind Surfing on the Columbia River at Hood River, Oregon.
9. See Multnomah Falls and walk to the top of it. The Columbia River Scenic highway goes by it and several other beautiful falls on the way towards Portland (this is not I-84).