Descending Bannock Pass, the railroad followed a narrow canyon into Idaho's Lemhi Valley and the small agricultural community of Leadore, some from Armstead. The G&P's repair shops were at Leadore, and it also marked a junction point for the railway. The main line continued northwest from Leadore for another , following the broad valley and the Lemhi River downstream through fertile farming and ranching land to the county seat of Salmon. Salmon was the line's terminus, and by far the largest town on the G&P route, with a 1910 population of 1,434.