In July 1859, Lieutenant John Mullan and 230 workers, soldiers, and teamsters began building a 624-mile wagon road from Walla Walla, Washington, through the Rocky Mountains to Fort Benton in Montana, the head of steamboat navigation on the upper Missouri River. Between Lake Coeur d'Alene and the Missoula Valley, they faced towering mountains, serpentine rivers, steep rugged hillsides, low swampy areas, deep ravines, and fallen timbers. Mullan's men built 47 bridges across the St. Regis-DeBorgia River between the base of St. Regis Pass and its confluence with the Clark Fork 28 miles east of here. Though primitive, the road was a triumph of engineering and later became important as an emigrant and freight route in western and central Montana, even though the section west of Missoula saw limited pioneer use because of the difficult terrain. Within a few years of its completion, most of the bridges had washed out and timber and landslides had blocked parts of the road, and by the 1870s through this area it was little more than a pack trail, though portions still survive on mountainsides overlooking Interstate 90. Near here, the railroad camp of Taft was founded in 1907 and became the operations center for construction of the Chicago, Milwaukee, St. Paul and Pacific Railroad's 8,750-foot tunnel through the Bitterroot Divide at St. Paul's Pass. More than 2,000 men worked day and night on the tunnel for a little over a year in a town crowded with saloons, gambling halls, and brothels; after the tunnel was finished, Taft was largely abandoned, then mostly destroyed in the 1910 forest fire, with the rest buried beneath Interstate 90 in 1962.