Flathead Lake (Salish: člq̓etkʷ, Kutenai: yawuʔnik̓ ʔa·kuq̓nuk) is a large natural lake in northwest Montana. The lake is a remnant of the ancient, massive glacial dammed lake, Lake Missoula of the era of the last interglacial. Flathead Lake is a natural lake along the mainline of the Flathead River. It was dammed in 1930 by Kerr Dam at its outlet on Polson Bay, slightly raising the lake level; the dam generates electricity. The hydroelectric has been owned and operated by the Confederated Salish and Kootenai Tribes since 2015. It is one of the cleanest lakes in the populated world for its size and type.