Elk River adopted in the 2nd Report of the Geographic Board of Canada, 30 June 1900, as labelled on Palliser's Expedition Map 1857-58. Originally described as "tributary to Kootenay River". Re-approved 2 December 1948 on Columbia River Basin manuscript 51, and description subsequently changed to "tributary to Lake Koocanusa".
Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office
On his second journey, 1811, David Thompson crossed the Athabasca Pass and followed a circuitous route to the mouth of the Columbia River; he called this the "Stag River." Labelled "Elk River" on Palliser's 1857-8 map (copy with BC Archives); labelled "Stag or Elk River" on Arrowmith's 1862 map of British Columbia.
Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office