You should know that the blackhills will be full of motorcycle riders for the annual Sturgis bike rally. I don't know if that is something that you're wanting to hit or not. It could be seriously cool or seriously uncool, depending on your views but one thing is for sure it is huge huge huge and I believe it happens at the end of July.
If you're looking for natural wonders and sites to see. I would suggest these:
Ride across the great salt flats on highway 50.
Ride the tioga pass in yosemite national park.
Ride trail ridge road in colorado
Ride to the top of Mt. Evans, CO - highest paved road in the world. 14,000+ ft.
Ride to the top of Pikes Peak, CO - another paved road to 14,000 ft.
Ride through Yellowstone National Park and see the Old Faithful geyser
Stop and see the Grand Canyon
Mesa Verde National Park has some cool cliff dwellings to look at
Cook your skin in the Mojave Desert or see Death Valley
See giant California Redwood trees
There are a few hot springs around Colorado, Wyoming, and South Dakota that you and the lady might like.
If you have time ride through the western half of Montana, it is gorgeous country
Depending on when and where or if you'll be in Nebraska, you could encounter the Sandhills Open Road Challenge featuring a 55 mile course of closed off highways. This happens in August.
Countless delicious microbreweries in the rocky mountains states especially
All of those places are west of the great plains states. I'm planning a western US route in June and most of those places are on my list. I've been scouting roads and sights to see for the last few weeks.
///Monster screwed with this post 12-04-2012 at 03:11 PM