"Kootenay River (not Kootenai, Kootanie, etc)" adopted in the 2nd Report of the Geographic Board of Canada, 30 June 1900, being the official spelling in British Columbia since 1864. Also Lake.

Source: BC place name cards, files, correspondence and/or research by BC Chief Geographer/Geographical Names Office.

Named after the Kutenai Indians who inhabit the region [the preferred modern name is Ktunaxa Nation.] Spelled "Kootanie River" on Palliser's 1857-58 map, then identified as "Flat Bows River" in his 1863 report; spelled "Kootenay" (river, pass, lake, etc) on Trutch's 1871 map; spelled "Kootenai River" in USA.

Source: BC place name cards, files, correspondence and/or research by BC Chief Geographer/Geographical Names Office.

Headwaters in British Columbia in the vicinity of 51° 04'20" x 116° 23' 45" on map 82N/1, then flows in a general southward direction on the east side of the Brisco and Stanford Ranges and continues southward into the Rocky Mountain Trench at Canal Flats (village) [at this place, the Kootenay River is less than 3km from Columbia Lake - the source of the Columbia River]; the Kootenay River continues in a general southward direction within the Rocky Mountain Trench, expanding into Lake Koocanusa and flowing across the BC-Montana boundary at 40" 00' 00" x 115° 11' 00" on map 82G/3. The Kootenai River [as spelled in USA] continues south through Lake Koocanusa pondage thence turns west and flows through Libby Dam in Montana and continues in a general northwesterly direction past Troy, Montana and Bonners Ferry, Idaho then northward back into British Columbia, flowing across the Idaho-BC boundary at 40° 00' 00" x 116° 30' 15" on map 82F/2; the Kootenay River continues in a general northward direction past Creston and expands into Kootenay Lake; from the lakes' outlet at the head of the West Arm, near Nelson, the Kootenay River continues in a general southwesterly direction a distance of 25km, flowing into the Columbia River at Castlegar. Total length of the Kootenay River is 780 km (508 km in British Columbia, 272 km in USA).

Source: BC place name cards, files, correspondence and/or research by BC Chief Geographer/Geographical Names Office.

McGillivray's River was the name given by David Thompson, when he passed this way in 1808, after his partners William and Duncan McGillivray. See McGillivray's Portage: The USA portion is labelled "Flat Bow River" on a map drawn by J.H. Young, Philadelphia, reproduced & circulated as Rand McNally's 1955 Christmas card.

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