Nine Mile Dam, also known as the Nine Mile Hydroelectric Power Plant Historic District, is a dam located on the Spokane River in the unincorporated community of Nine Mile Falls, Washington, USA. Constructed in 1908 at a cost of between $800,000 and $1,000,000, it created the Nine Mile Reservoir. The dam is built of cyclopean masonry (large blocks of granite set in concrete) and measures 363 feet across the top and is 58 feet high. It was originally designed to supply power to the surrounding Spokane area, and today, it continues to serve as a hydroelectric plant. The community around the dam straddles the Spokane River, approximately nine miles away from downtown Spokane, at the location of a former falls which has been replaced by the dam. Additionally, there are various hiking trails near the dam, including a 4.5-mile out-and-back trail and a 1.6-mile loop trail, both of which provide opportunities to explore the surrounding natural beauty and learn more about this historical landmark.