The Kerr Dam, a 204-foot-tall concrete arch dam on the lower Flathead River eight miles southwest of Polson [1], controls the water level of the lake and the lower river. It was built during the Depression and opened in 1939. It is operated by the Montana Power Company, which leases the land from the Confederated Salish and Kootenai Tribes.
The lease payments, which amount to $9.4 million annually, are a major part of the tribes’ economy. Reach it by heading west on 7th Avenue to Highway 354 and following the signs. (This makes a nice bike ride if you don’t mind rolling hills with one steep climb.) A long flight of steps leads to a vista over the dam before the road goes down to the power station.
Links:
[1] http://www.moon.com/destinations/montana/missoula-and-northwestern-montana/flathead-lake/polson