Everyone else has beat me to it!
Since you are asking, I'm betting that you are looking for new ideas on places you haven't been. That probably rules out the desert west.
For my money, and since you are talking as far east as OH, the UP of Michigan is a MUST. You could easily spend the entire time there depending on your personal interests.
Banff/Jasper/Calgary is another place you could do the entire trip imo. Great time of year for it. The trip up in itself would be grand.
I may be jaded from growing up in east TN, but the Smokies cant compare to the Rockies in any form or fashion except traffic, cheesy roadsides, and tourist volume in which they beat the Rockies by many orders of magnitude. But they are fantastic in mid-late October when the leaves turn.
When you narrow it down, be sure to post where so that we can get more specific in places to go, things to do.