US 12 in northern Idaho along the Clearwater and Lochsa Rivers is one of the most scenic highways you will ever drive. From Lewiston east to Kamiah there is some traffic, not really all that much though. From Kamiah east to the MT/ID border at Lolo Pass is where you'll fall in love with nature again. Just take it easy, pull over on the pullouts once in awhile to let vehicles following you get around, watch for bicycles on the curves, and enjoy the trip. There are some good USFS campgrounds along the way, two of our favorites are Wendover and Apgar, but Apgar can be a little tight for big rigs. Have been driving this route off and on since the paving was completed 50 years ago this summer. Stop at the Visitor Center at Lolo Pass. Another good park to spend a night is in Lewiston: Hells Canyon SP along the Snake River not far from the confluence of the Snake and Clearwater Rivers. Some good blackberry picking around MP 102 or thereabouts. US 12 is defintely the way to go to Missoula from Lewiston, forget I-90 (too much traffic and nothing to enjoy).