The Eagle Nest Tunnel/Bridge

One of the most scenic and visually stunning locations along the Milwaukee Road's Pacific Coast Extension was a rather small, simple deck plate girder bridge and tunnel at a location known as Sixteen, Montana. What became known as Eagle Nest Tunnel, located along the main line between Harlowton and Three Forks, the bridge and tunnel are spectacular for how the entire project was built; the tunnel was cut into a small cliff-face and empties out directly onto the bridge which spans a small creek. With the Milwaukee Road's abandonment of its Extension in 1980 this section of the line lies dormant today and has not seen a train in over 30 years.

Few rail lines, let alone railroads, have garnered such interest, intrigue, and awe as the Chicago, Milwaukee, St. Paul & Pacific Railroad's Pacific Coast Extension, even 30 years since it was abandoned. Unfortunately, the best engineered rail line through the rugged Cascades could not save it from the inept decision making of management at the time and it is now but weeds and trails, a vital transportation artery no longer available to shippers and the American economy.

In 1901 the first surveying work began and it was estimated the more than 1,400-mile western extension would cost the railroad around $45 million adding more than 25% to its total system mileage. However, four years later this number was readjusted to $60 million. What made the extension so terribly expensive was partly due to the right-of-way costs. Unlike the GN and NP the CM&StP was not given free government land grants and had to both purchase all of its land from private landowners as well as take over a number of small, new, or floundering railroads across the region. Amazingly, in just three short years the entire extension had been completed and on May 19, 1909 a Golden Spike was driven at Garrison, Montana commemorating the opening of the new route.

Eagle Nest Tunnel Specifications

Tunnel Number Milepost Height Width Length
#41408.519'-4"14'-5"370 Feet

Unlike much of the Pacific Coast Extension, the section between of the route between Harlowton and Lombard, Montana, a distance of about 91 rail miles did not require extensive surveying and preparatory work, as the Montana Railroad had already built a route through the region. While the line, originally built between 1894 and 1900, was not up to the Milwaukee Road's specifications it did offer an excellent base from which to work. As such, the Milwaukee Road entered a trackage rights agreement with the Montana Railroad in December, 1907 for 99 years although just over two years later in January, 1910 the latter company sold the route directly to the CMStP&P. Between 1906 and 1910 construction crews (which was handled by contractors Dittmar, Breadbury & Weitbrec and McIntosh Bros.) worked to upgrade the route to Milwaukee Road's specifications. In doing so they straightened curves and eased grades, which usually consisted between 1% and 1.7%.

In doing so, surveyors and engineers cut a route through Sixteen Mile Canyon, which proved to be difficult and laborious with steep canyon walls and solid rock making up much of the area. The route through the canyon covered several miles and the location of Eagle Nest Tunnel and bridge crossed the Sixteen Mile Creek. The bridge itself was a little under 300-feet in length and only stood about 100-feet in height to the rail head and its greatest. The tunnel was also rather small, being just a few hundred feet in length (which was quite small for most tunnels across the route!) although it was cut through solid rock. 

While Eagle Nest Tunnel was open cut-stone along its east portal next to the bridge, the west portal featured a standard concrete approach abutment. What made the location so impressive was simply the way it was engineered with the tunnel cut directly into the mountain face and spilling directly onto the bridge spanning the creek bed. To make train operations even more interesting for sightseers and railfans to witness, if they wanted to make the arduous journey to the remote location, was the electric locomotives operating on the line through June, 1974. As it turns out, the Milwaukee Road found operating through Sixteen Mile Canyon quite difficult with a narrow right-of-way and unstable rock located in the area. The railroad would line most of the route through the canyon with fencing and warning lights in the event of rock slides, which were not uncommon.

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