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Cascade Tunnel - the Longest Railroad Tunnel in the US

Cascade Tunnel Entrance

By Roni Freund - 2020 marks the 120th anniversary of an engineering marvel (pun intended!) when, in December of 1900, the longest railroad tunnel in the US was opened for train travel over Steven’s Pass. 

Pacific Northwest Rail History

Map of Stevens Pass Switchbacks

Train travel over the Cascade Mountains began in the late nineteenth century when the Great Northern Railroad laid tracks over the 4,000-foot summit of the Stevens Pass. The grade was so steep they had to build switchbacks on both the eastern and western slopes. A thousand-foot spur line for each switchback was needed for the train to stage while the switch was thrown to continue the climb to the next section. The trains would travel thirteen miles of track to move 3 miles toward its destination. 

In 1897 construction of the Cascade Tunnel began. It's goal was to eliminate the complicated and time-consuming switchback system. The original tunnel was 2.6 miles long, and entirely lined with concrete. There were also seventeen “snow sheds” constructed over the rail line as it climbed toward the tunnel. The snow sheds were designed to deflect avalanches over the rails. You can still see remnants of many of these sheds when you drive over Stevens Pass in the summer. You can also hike the Iron Goat Trail and traverse part of the old railbed, including switchbacks. 

While the tunnel eliminated the steepest climb over the pass, there was still an incline especially for the eastbound train. Thick smoke would fill the tunnel with deadly fumes, and after reports of passengers and crew becoming ill, a new solution was proposed: the trains would be pulled through the tunnel by electric locomotives. 

Tumwater Dam

Tumwater Dam

Construction of a complete hydroelectric plant to generate power for the electric locomotives began in 1907. It was completed in 1909, and at that time it was the largest hydro-electric project west of Niagra Falls. Four electric locomotives were powered by trolley lines and pulled freight and passenger trains through the tunnel. 

Several features of the project are still visible along the Cascade Loop today. The Tumwater Dam created a reservoir which directed water to the generators at the power plant. The water ran through a 8-1/2 foot pipe made of wooden staves and held together by heavy steel cables. The powerhouse was made  of concrete and brick and it housed three waterwheels and three 2,000 kilowatt generators.

Today there is a fish ladder at the dam so adult salmon and steelhead can return to their spawning grounds. If you pull in to view the area, you might witness fish and wildlife personnel counting fish. They invite your questions!

The reservoir behind the dam is called Jolanda Lake. It is a favorite stop for viewing fall colors and spawning salmon, and also ducks and Canadian geese. Pull over across the highway from The Alps Candy Store. Watch the trees across the lake for a resident bald eagle pair.

Penstock Bridge

Pipeline Bridge over Wenatchee River

A mile downstream from the Tumwater Dam, the Penstock Bridge carried an 8 1/2-foot pipe across the Wenatchee river. 

The Penstock Bridge is on the National Register of Historic Places. It is a riveted steel Baltimore Petit truss, built by the Great Northern Railroad Company around 1909.

Penstock Trail

The penstock bridge remains, and the trailhead parking area is where the concrete building once stood. 

The Penstock Trail (aka Old Pipeline Trail) is a popular 2.4 mile hiking trail. The mostly level trail crosses the Penstock Bridge and follows the Wenatchee River upstream toward the Tumwater Dam. 

In the spring there may be some water across the trail. Near the end of the trail there is a tunnel where you can still see remains of the early 8.5 foot pipe. The wood has decayed, but the heavy steel cable that held the staves can still be seen.

The New Tunnel

In 1929 the new Cascade Tunnel was constructed, less than two miles to the south, and at a lower elevation than the original tunnel. It is 7.8 miles in length, and still in use today. About this same time Great Northern built another rail line through the Chumstick Valley from Leavenworth to the current Cascade Tunnel entrance. This became the main route and the Tumwater Canyon was no longer used for freight or passenger trains.    

Beginning in 1956 locomotives became diesel powered, so the hydro-electric power was no longer needed. The power plant was dismantled, and the rail lines were removed. Much of Highway 2's Cascade Loop Scenic Highway which runs through the Tumwater Canyon follows the old railbed. 

First EV-friendly Scenic Byway in the US

In 2011 Highway 2 from Everett over Stevens Pass to Wenatchee became the first EV-friendly Scenic Byway in the US. EV Charging stations installed at the top of the pass were the keystone of the project, which brought electrically powered travel over Stevens Pass full circle with environmental-minded problem solving. See a list of EV Charge stations around the loop at

Wellington Disaster

Wreckage of Train Car after Wellington Disaster

A year after the hydro-electric power plant was completed, in late February of 1910 a deadly storm trapped two trains just east of the Cascade Tunnel entrance. After several days waiting for the snow to stop falling and for help to arrive with supplies, a bolt of lightning hit the mountain tops and the rumbling thunder caused an avalanche that knocked the trains off the rails and into the river gorge 150 feet below. 

A massive rescue effort took place, but many lives were lost. Read more about our Wellington Disaster blog here

Penstock Bridge with generator building in background.

Special thanks to for the historic photos and Cascade Tunnel opening image.

Contemporary photos by Pete Freund Photography.