Best Kept Secret: Penstock Bridge in Leavenworth, Washington

All photos taken by Corey Pruitt, used with permission.

Recently, a fellow bridgehunter Corey Pruitt found this bridge with three of his companions. Located outside Leavenworth in Washington, the bridge looks like a typical Baltimore through truss bridge that had once carried a railroad but is now part of a hiking and biking trail. However, when looking at the bridge’s portal bracing, it looks rather different:


Looking into the bridge via tunnel-view, one can see a decking that rather looks like an aqueduct than a railroad:


As you can see, this through truss bridge is rather unusual for its use, even though the design. To find out more about this bridge, the author and another pontist did some research only to find that this structure, now a rails-to-trails crossing, was built by the railroad company but was used for another purpose, which was to provide Hydroelectric Power?!!!

Here’s a look at the history of the Historic Penstock Bridge over the Wenatchee River near Leavenworth, Washington.

The bridge is a riveted steel Baltimore Petit truss. It was built in 1907 by the Great Northern Railroad Company as part of the Tumwater Hydroelectric Plant. The hydroelectric plant was constructed in 1909 to power Great Northern trains from Leavenworth to Skykomish. The hydroelectric installation, which was an extensive system that required conductors and additional power stations, was built to power the Great Northern trains over a 57-mile mountain division from Leavenworth to Skykomish. The water, which was the power source for the electrification of the tunnel, was transported approximately two miles by a penstock from a 250-acre storage site to the powerhouse. The seven-panel bridge was constructed to carry the 8.5-foot-diameter penstock from the south bank of the river to a surge tank at the corner of the powerhouse. Most of the penstock was wood stave pipe; however, the last 952 feet of pipe, part of which passed through the bridge, was constructed of riveted steel. The penstock pipe through the bridge has been cut, to enable the bridge to be used as a pedestrian walkway. The bridge is one of the early examples of a riveted steel Baltimore Petit truss and remains as one of the few extant reminders of the early attempts to electrify the railroads through the Cascade Mountains. The bridge was listed on the National Register of Historic Places in 1982 (NRHP No. 82004196)

It is highly recommended to not only see the bridge, but also take the Penstock Trail because of its gorgeous landscape and many activities you can do along the way. A link will show you the trail in its entirety. 🙂


Special thanks to Dave Denenberg for the help in the research and Corey Pruitt for the use of the photos.