Assuming going through Yellowstone might be too time consuming and that you are mostly looking for interesting driving route....
-Keystone to Custer
-Custer to Newcastle, WY
-Newcastle to Casper via WY-480 across Thunderbasin National Grasslands
-Idaho Falls to Mt. Home via US-26 and Craters of the Moon
-I-84 to Portland via Columbia River Gorge (super scenic)
-Portland to Astoria via I-5 and US-30 (US-30 part very pretty)
-Astoria to Long Beach via Coast Highway 101
Just a tad under 1,400 miles so three comfortable sub-500 mile days. Suggested stop points...
-Dubois, WY (or Riverton, WY)
Not sure how evenly these divide the miles. Stopping at Dubois or Riverton means being able to get to Tetons in morning with sunlight from behind lighting up the peaks.
Also check the Road Trip forum.Edited: 27 June 2012, 18:38
That's a great route Sequim has given you. If you can take 4 days for this trip and enjoy more of the places on your way. If you decide to take I90 first there's a scenic byway us12 that leads from Missoula to Lewiston and on to Kennwick called Lewis and Clark Trail. That goes on to Portland via Columbia River Gorge.
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