American Airlines has round-trip flights from Dallas (DFW) to Portland, Oregon or Seattle (PDX, SEA) for $151-$161, NONSTOP. Flights October to December. Departures on Tuesday, Wednesday, and Saturday. Extended weekends available. Origin/Destination reversible.
Carry-on bag is allowed for free. Fares are Main Cabin, not Basic Economy. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.