Listed on the National Register of Historic Places on 12/6/1990.

Closely associated with the development of electric interurban railroads in the Inland Empire, the Nine Mile Hydroelectric Power Plant Historic District is an early and well preserved example of a power plant specifically developed in conjunction with a transportation network. The plant was built in 1906-1908 in a remote canyon on the Spokane Rivers, and includes a powerhouse which is structurally integral with the dam. When complete, the plant provided power for the Spokane and Inland Empire Railway system, a network that provided freight and passenger service along 250 miles of track radiating from Spokane south to the Palouse wheat district and east to Coeur d'Alene, Idaho. In addition, the plant supplied surplus power to small communities along the route. In 1925, the plant was purchased by Washington Water Power Company, which a few years later constructed a small workers' community at the site, composed of ten brick bungalows in the Craftsman and English Cottage styles. The site is among the best preserved hydroelectric plants in the state, and one of the most significant extant properties associated with interurban railroads in Washington.