Shoshone Transmission Line

The Shoshone Transmission Line was an early and notable electric power transmission line, now recorded on the List of IEEE Milestones. The line takes its name from the power plant at its west end which generates hydroelectric power below the Shoshone Rapids in Glenwood Canyon.

The line began service on July 17, 1909, conveying power from the 10 MW Shoshone Hydroelectric Generating Station, outside of Glenwood Springs to Denver, serving substations in Leadville, Dillon and Idaho Springs. At the east end of the line, it was connected to the utility's Boulder Canyon Hydroelectric Plant powered from the Barker Meadow Reservoir. In the event of a break in the line, either power plant could supply customers along the line.

As originally built, the line was 153.4 miles long, crossing the Continental Divide at Hagerman Pass (at altitude 12,055 feet), Fremont Pass (at altitude 11,346 feet) and Argentine Pass (at altitude 13,532 feet). For many years, this was the highest electric power transmission line in the world. The three-phase line operated at 90 kV and was supported 1400 steel towers 44 feet high on an average spacing of 730 feet.

A secondary power line from the backbone of the Shoshone line connected it to a steam generating station at Leadville, as well as to many of the mines in the Leadville region. At Dillon, a secondary line served the numerous gold dredges of the Breckenridge placer mining district. Connections were also made to smaller hydroelectric plants at Dillon and Idaho Springs.

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