Jim,
For convenience, Lewiston is the choice - depending upon where you are headed. You could probably find better prices into Spokane, WA or Boise, ID. Lots of airlines with those two cities. Lewiston only has Horizon Airlines the last I knew, a partner with Alaska Airlines.
Boise to Lewiston will take 5 to 5 1/2 hours driving. Spokane to Lewiston around 1 3/4 to 2 hours. Both routes are two lane roads but good.
I can't help you with ticket prices, which is what you were after in the first place.