Recommended route from Portland, OR to Glacier NP?

Check out Glacier Meadow RV Park in Essex MT between east and west Glacier.
Reasonable rates, no sewer but they have pump service included in their site rate. Limited cell service but they do have a booster in the pavillion. One of our favorite parks!! Be sure to visit the Isaak Walton Inn in Essex. If you're up for an adventure down a dirt dusty road, go see Polebridge Mercantile in Polebridge MT and get a huckleberry bear claw at the bakery!