Madison Dam is a hydroelectric dam on the

Madison River The Madison River is a headwater tributary of the Missouri River, approximately 183 miles (295 km) long, in Wyoming and Montana. Its confluence with the Jefferson and Gallatin rivers near Three Forks, Montana forms the Missouri River. Th ...

Madison County, Montana Madison County is a county in the U.S. state of Montana. As of the 2020 census, the population was 8,623. Its county seat is Virginia City. The county was founded in 1865; at the time it was part of the Montana Territory. Geography According t ...

, in the southwestern part of the state. The timber-crib dam was constructed in 1906 as a replacement for a similar 1901 dam and powerhouse on the same site. The dam is high and long at its crest, placed into the narrows of Bear Trap Canyon. As one of eight PPL Montana hydro projects, it has a generating capacity of in a run-of-the-river configuration. Montana Power Company acquired the dam in 1912 as part of a merger,

PPL Corporation PPL Corporation is an energy company headquartered in Allentown, Pennsylvania in the Lehigh Valley region of eastern Pennsylvania. The company is publicly traded on the New York Stock Exchange. History Pennsylvania Power & Light was founded in 1 ...

purchased it in 1997 and sold it to

NorthWestern Corporation NorthWestern Corporation owns NorthWestern Energy, a utility company that serves South Dakota, Nebraska, and Montana that is based in Sioux Falls. , the company serves approximately 718,000 customers. The company's corporate headquarters are loc ...

in 2014. The reservoir it creates, Ennis Lake, is long and has a maximum storage capacity of . The lake is relatively shallow and warms significantly during the summer, which tends to decrease fish populations. The lake supports recreational fishing for brown trout and rainbow trout, camping, boating, and white-water rafting in Bear Trap Canyon downstream (north) of the dam.

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* {{Authority control Dams in Montana Reservoirs in Montana NorthWestern Corporation dams Buildings and structures in Madison County, Montana Dams completed in 1906 Historic American Engineering Record in Montana Landforms of Madison County, Montana 1906 establishments in Montana