Lake Koocanusa is a 90 mile-long impoundment of the Kootenai River in northwest Montana. The lake is formed by damming of the Kootenai River by the Libby Dam. Half of the lake is in Canada and half in the United States. The name of the lake is formed by the first three letters of Kootenai, Canada, and USA. The closest towns are Libby and Eureka. The lake contains Kokanee Salmon, Rainbow Trout, and Bull Trout. The lake has a noted fall / winter trolling fishery for large Rainbow and Bull Trout.