For the South West part of the trip you are okay. For the North West part of the trip you'll be a bit late in the year. Cold and snow set in pretty fast in the NW USA.
My suggestions are these:
1. Do the trip in reverse. The NW first, then come south.
2. Get a book on the National Parks, Monuments and Historical Sites. This will get you started.
There is too much to see to post here. When you have specifics, please post.
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