Montana and Washington camping spots

Any recommended spots along this route? [URL]https://goo.gl/maps/qbBX7fiuM3qea4oJA[/URL]

I have traveled most of that route many times. But, I am a motel guy, not a camper. I do know there is a very nice KOA in Winthrop, Wa. It is right on 20. Can't miss it. Winthrop is your last reasonable size place to stay and have good restaurants before going over the North Cascades.... Jim