was largely built to the mainline standards of the NP. A golden spike celebration was held in Salmon that May 18, even though portions of the line—including the tunnel under Bannock Pass—were still being completed. Regular passenger and freight service on the G&P began soon thereafter. Optimism and rumors concerning further expansion of the G&P persisted through 1910. McCutcheon had promised that the line would be extended northward from Armstead to Dillon, Montana that year, the first step in completing a connection to the NP's trackage at nearby Twin Bridges. No further construction took place, however, in part due to G&P legal difficulties in securing right-of-way between Armstead and Dillon. Simultaneously, though, the NP began to realize the engineering difficulties and limited economic potential of its proposed Salmon River route, and local G&P officials began to discover that the local traffic potential was actually far less than anticipated. Consequently, the hopes for future expansion of the G&P soon faded, and the line was never extended beyond either Armstead or Salmon. Route The route of the G&P was remote, thinly populated, and often rugged. The line began at the small hamlet of Armstead, Montana, a station stop on the Oregon Short Line Railroad's route between Idaho Falls, Idaho and Butte, Montana. (The Oregon Short Line was a long-time subsidiary of the Union Pacific Railroad, and was later absorbed into that system.) Armstead was in a high valley of the Beaverhead River, in a region known for livestock grazing. The G&P maintained a small yard there, and it was the site of the railroad's corporate office. From Armsted, the railway headed almost due west, traversing a thinly-populated ranching region known as Horse Prairie. The area provided additional livestock traffic for the railroad, and there were mines in the nearby mountains. Substantial areas of cut and fill were required as the railroad ascended the prairie. The railroad curved southward near the western end of Horse Prairie. and began its ascent of Bannock Pass. Bannock Pass, on the Idaho-Montana border and the Continental Divide, was by far the most substantial obstacle encountered by the G&P. The pass itself is at an elevation of , some higher than the center of Horse Prairie. Temporary trackage was built over the top of the pass during the G&P's construction, but a tunnel beneath the pass was clearly needed for the railway's permanent use. Since a tunnel to