Tunnel Number Twenty: The St. Paul Pass and the Milwaukee Road

By Editor

Mineral County, Montana / Shoshone County, Idaho, 1906-1908

The grade was not to exceed 2.2 percent. That was the specification, and the surveyors who went into the Bitterroot Mountains in August 1906 with their transits and stadia rods and surveying chains and barometers understood that the specification was not a suggestion. They covered 1,400 miles of terrain in order to select 240 miles of route, which is the kind of arithmetic that tells you something about the difficulty of the country.

The Milwaukee Road was the last transcontinental railroad built in the United States. It came late to the Pacific Northwest, and it came through country that the Northern Pacific and the Great Northern had already crossed by easier routes. The Milwaukee's engineers knew this. They surveyed anyway, because the company had committed to the Pacific Extension, and the Pacific Extension required crossing the Bitterroot Range, and crossing the Bitterroot Range at a grade of no more than 2.2 percent required a tunnel.

The tunnel they built was 8,771 feet long, which is 1.66 miles, which is long enough that you cannot see the light from one portal while standing at the other. It was bored through the Bitterroot Range at an elevation of 4,150 feet above sea level at the Montana portal, and it crossed the Continental Divide at St. Paul Pass, which sits at 5,162 feet. The surveyors and engineers achieved a grade of 1.7 percent from Haugan on the east to Avery on the west, which was better than the specification required and worse than the Northern Pacific and Great Northern grades through their respective passes. The men who built it knew the difference.

Grading toward the pass began from Missoula in July 1906. Work began on both approaches to the tunnel at approximately the same time. Heavy boring began in 1907. The tunnel was officially completed in December 1908. The Milwaukee Road numbered its tunnels from east to west, and this one was Tunnel Number Twenty. The contract work was done by Winston Brothers Company of Minneapolis, with primary subcontract work carried out by four other firms. The men who actually drove the bore are not named in the company records.

At the east portal, during construction, a town grew up. The Milwaukee Road called it East Portal. The men who lived there called it Taft, after William Howard Taft, who visited the work camp while serving as Secretary of War under Theodore Roosevelt and described the place as a sewer of sin and a sore on an otherwise beautiful national forest. The town named itself after him anyway, which was either a joke or a tribute, depending on your view of the man. Taft had between twenty and fifty saloons at its peak, a population of approximately three thousand, and a second profession after railroad worker that the company records do not specify but the county records do. In the spring of 1909, as the construction wound down, seventeen bodies were found when the snow melted. The town burned in the Big Blowup of 1910, and the forest rangers made sure it was not rebuilt.

The tunnel itself survived. In 1914 and 1915, the Milwaukee Road electrified the Rocky Mountain Division, running overhead wire from Harlowton, Montana, to Avery, Idaho, a distance of 440 miles. Electric locomotives replaced steam through the tunnel, which solved the ventilation problem that had made steam operation through long tunnels a matter of some delicacy. The electrification was, by any technical measure, a remarkable achievement. It was also, financially, a disaster, because the Milwaukee Road had built its Pacific Extension through country that did not generate sufficient freight revenue to service the debt, and the electrification added to the debt without solving the underlying problem.

The Milwaukee Road abandoned its western trackage in 1980. The tunnel sat empty for twenty years. It has since been reopened as a rail trail, part of the Route of the Hiawatha, and thousands of hikers and cyclists pass through it each year. The overhead wire structures, the gallows frames that held the catenary for the electric locomotives, still stand along the approaches. The grade is 1.7 percent, which is gentle enough for a bicycle.

The men who specified that grade, and the men who achieved it, would have considered that a satisfactory outcome.

See also

• St. Paul Pass Tunnel, Wikipedia article with full technical specifications
• Milwaukee Road electrification, the Rocky Mountain and Coast divisions
• Route of the Hiawatha, the rail trail that now uses the tunnel
• Taft, Montana, the construction boomtown at the east portal