You did not say your intention at first...

Go to NPS.Gov and check out the national parks that on your route.

Grand Canyon is the 大峡谷

Get a full-size map, glance the horizonal line between SEA and NYC - and move up/down accordingly, you will see the nearby National Parks along that line. Then go to U.S. government's website, NPS.Gov to check out each park on the route, get a rough idea, then come back to ask Qs here. Would be easier to get a whole picture than piecemeal information.