Property Type: Institutional
Neighborhood: The Boise River Project  |  County: Ada  |  Building Status: Public  |  Year Built: 1912  |  Architectural Style: Romanesque Revival
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Diversion Dam, located 7 miles southeast of Boise where the Boise River and the New York Canal divert, serves an important part in Boise and its history. The dam originally served as a dam to separate the Boise River from the New York after being built in 1908. However, in 1912, the powerplant was built to provide power to the construction of Arrowrock Dam and after that more than 2,500 homes in the Boise Valley.

In 1976, the Diversion Dam was recognized on the National Register of Historic Places because of its excellent condition of original parts. In 1983 the dam was placed on reserve but in 2001 received a renovation that renewed parts and allowed the power plant to work again.

Although not an architectural marvel, it does have significance. the Dam is largely Romanesque in its “rubble concrete weir-type structure” that includes Italianate style flares that extend from the top of the overhang. The material was also used to blend into the surrounding area of the cliffs.

Interestingly, when the building was renovated in 2001, builders found themselves with a challenge when they learned the building was on the National Register Historical Places and they were forced to keep some original parts instead of completely gutting the entire space to restart the project.