Chief Joseph Dam is a 5,962 foot (1,817.2 m) long, run-of-the-river
hydroelectric dam. It is named in honor of the famous Nez Pierce
Indian chief.

Installation of the initial generating units was completed in 1958.
Eleven additional turbines were installed between 1973 and 1979,
and the dam and lake were raised 10 feet (3 m), boosting the
capacity 2,620 MW, making Chief Joseph Dam the second largest
hydropower producer in the United States.

With 27 main generators in the powerhouse, it has the hydraulic capacity
of 213,000 cubic feet per second (6,030 m³/s).

from: Wikipedia