Question: The St Regis River begins at Lookout Pass in which mountain pass on the Idaho/Montana border? 
Sentence (from "Lookout Pass"): In the Coeur d'Alene Mountains of the Bitterroot Range, the pass is on the border between Idaho and Montana, traversed by Interstate 90 (formerly U.S. Route 10) at an elevation of 4710 ft above sea level.
Relevant evidence: No