Thompson Falls Dam

Thompson Falls Dam is a concrete gravity dam across the Clark Fork River, built between 1910 and 1914 by the Montana Power Company. It stands about 73 feet tall and backs up a reservoir extending several miles upstream into the valley. The dam is still active, generating hydroelectric power for the region, and you can see it clearly from the old bridge or from the bank near the state park.

The site is worth a stop to understand the trade-off the dam represents. What was gained — a stable reservoir for fishing and recreation, reliable electricity for a remote county — came at the cost of the actual falls that made this canyon remarkable in the first place. The calm water above the dam is pleasant, but early photographs of the falls make clear that something genuinely spectacular was lost.

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A story
The original Thompson Falls — a series of cascading rapids on the Clark Fork — were drowned when the dam was completed in 1914. David Thompson himself described them in his journals as one of the most striking features of the river. The town took its name from those falls, so the dam effectively erased the landmark that gave the place its identity.