Hells Canyon Dam is a concrete gravity structure on the Snake River (river mile 247) in Hells Canyon on the Idaho-Oregon border. The dam impounds the Hells Canyon Reservoir. It is the third and final hydroelectric dam of the Hells Canyon Project, which includes Brownlee Dam (1959) and Oxbow Dam (1961), all built and operated by Idaho Power Company. The Hells Canyon Dam powerhouse contains three generating units, with a total nameplate capacity of 391 megawatts. Power generation began in 1967 with 2 units and added the third unit in 1968.