What are some great places to sight-see between new york and california?

me and 2 of my friends plan on taking a big trip from new york to california. the states we are planning to visit are ohio (dont know where yet), tennessee (nashville), mississippi (any suggestions?), louisiana (baton rouge, new orleans), texas (houston, san antonio, el paso) new mexico (suggestions for south of new mexico?), arizona (phoenix), and california (san diego, los angeles, monterey, and san fran). can someone tell us some sights we should see along the way? or other towns we should visit near these areas? we havent experience much of america yet and really want to see A LOT! we need some advice! anything you can give will be helpful! thanks!