Max elevation: 4798 ft / 1462 m Min elevation: 38 ft / 11 m Elevation change: 4760 ft / 1451 m
Max grade: 6.7% Min grade: -6.3% Steepness score: 38 + 673 + 6151 + 15 = 6877
Distance: 475.42 mi / 765.12 km Travel Time: 7 hours 23 mins
It looks like one possible route that might be flatter would be to go through Dickinson, but make sure you double check everything if you're planning a road trip.
Elevation data comes from different sources and may not reflect true
driving conditions, so talk to other RVers if you're concerned about
steep grades. If you're planning to drive in the winter and you want to avoid snow, check the road conditions from Seattle to Missoula. You can also view a 3-D map of Seattle elevation or Missoula elevation.
These are some of the possible roads along this route. Use the GPS in your car to verify all driving directions. If you're looking for campgrounds along the way, search for RV parks between Seattle and Missoula.