Having family in RAP, NW usually provides the cheapest routing there. Coming from the east coast, MSP is usually easier to get into and out of than SLC/DEN/ORD (the other connecting cities into RAP) - they always seem to deal with bad weather the best, plus ATC isn't too overloaded up there.

The product isn't ideal - DC9 for the MSP-RAP leg typically - but it's not that big of a deal.