The earliest recorded European-Canadian presence in the project area was around 1810-1811 when fur trader David Thompson of the North West Company (NWC) explored the area and several NWC trading posts were established throughout the wider region, including Fort Spokane which became a center of trade for this region. In 1824, three years after the merger of the NWC with the Hudson’s Bay Company (HBC), Governor George Simpson of the HBC travelled by way of the South Saskatchewan River and Athapasca Pass to the Columbia River and then down to its mouth. This route, subsequently known as the "York Factory Express", brought additional fur-trading traffic through the Arrow Lakes/Columbia River areas. Fort Colvile, established by the HBC in 1825 at Kettle Falls on the Columbia River, replaced Fort Spokane as a center for fur trading activities in the HBC’s "Colvile District" (which included the entire present study region). By the late 1830s, the HBC had built a satellite of Fort Colvile, called "Mckay's House" or "Fort of the Lakes", in the vicinity of Arrowhead at the upper end of Upper Arrow Lake. Another HBC post, Fort Shepherd, was built in 1856-1857 on the west side of the Columbia River about 1.6 km north of the international boundary. This was done to allow the HBC to continue their trade in this region, as it was anticipated that Fort Colvile would be closed by American authorities. Fort Shepherd operated sporadically until 1870.

Missionaries followed the fur traders into the upper Columbia. In 1838, two French Canadian Catholic priests, Modeste Demers and Norbert Blanchet, travelling with an HBC fur brigade, passed through the Arrow Lakes where they remained for nineteen days and baptized a number of Lakes (Sinixt) aboriginal people at the "Fort of the Lakes". Additional baptisms and religious instruction were provided in 1846 by another priest, Father P.J. De Smet, who spent several days among families of Lakes people "belonging to the station of St. Peter" camped on the borders of Upper Arrow Lake. Also in 1846, De Smet selected a site for a church at the Kootenay-Columbia confluence (although no church was ever built.)