Adopted 17 June 1968 by the Canadian Permanent Committee on Geographical Names, and by the United States Board on Geographic Names.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

A reservoir on Kootenay River [spelled Kootenai in the United States] created behind the Libby Dam in Montana. Almost half of the 85-mile-long Lake Koocanusa is in British Columbia, extending upstream from the international boundary to Wardner. At full pondage, the level of the lake is the 2459 ft contour.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

When a name had to be found in 1968 for the reservoir, the province of British Columbia suggested 'Kitunaha', the name of the Indian tribe originally occupying the area. This was strongly opposed by Jack Davis, then-minister without portfolio in the Trudeau government, who found the name unpronounceable. The Historical Association of East Kootenay suggested the name Lac Morigeau after the first white settler in the region. "Koocanusa," a hybrid name combining Kootenay - Canada - and USA, was the winning entry in a contest won by Alice Beers of Rexford, Montana; said to have been well-received by the settlers and residents who faced relocation because of the new reservoir.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office