Snaking its railroad down the western side of the Bitterroot Mountains, the Milwaukee Road dug 16 tunnels to maintain a uniform grade down to Avery. The tunnels were dug largely by hand using sledgehammers and hand drills, though in some cases steam-powered drills and steam donkey engines were hauled to the work site to speed the digging. The massive job took three years and the toil of hundreds of men before the St. Paul Pass Tunnel was opened in March 1909. Between Roland and Avery, the 16 tunnels ranged from 178 to 1,516 feet long, with a total length of 8,557 feet, and nine of them are on the Route of the Hiawatha.