Northwestern US state (6)
(Other definitions for idaho that I've seen before include "silver-mining state" , "State of NW US" , "US location" , "One of 22 Across, capital Boise" , "NW state of USA" .)
(Other definitions for oregon that I've seen before include "US state, capital Portland" , "America's Beaver State" , "State of north-west US" , "US region" , "area of the US" .)