We ;just returned from 22 days on the road and visited Glacier NP. We stayed at Polson RV resort in Polson Mt. for 3 nights. Very nice park next to the KOA. I think same folks own both. Get high on the rise to see the lake. We rented a lot with outdoor kitchen and thoroughly enjoyed it. Weather was outstanding.
It is about 1.5 hour drive into the Park from Polson. Polson is probably the nicest RV park in the vicinity but by the time you drive thru the park and back to Polson you will be exhausted. Traffic is slow although Montana speed limits are 65 to 70 mph on two lane roads.
We stayed in Spearfish, SD to visit Mt Rushmore, Crazy Horse, and Devils Tower .
Buy some fresh cherries – they are delicious!! You had better hurry – the park will be closing soon.