Decision in 18th Report of the Geographic Board of Canada, 31 March 1924. Drains into Okanogon River in Washington State.

Source: Canadian Geographical Names Database, Ottawa

"Similkameen River (not Castle nor Roche)" confirmed in the 1930 BC Gazetteer; 95 miles in BC, tributary to Okanogan River just below Osoyoos Lake in Washington State.

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

The original Indigenous name was recorded as being Similkameugh, meaning unknown, but said to be descriptive either of the people or their territory. No connection with Tulameen, despite the common ending, the original name having been forced by the whites into the same phonetic groove as Tulameen, in much the same way as Kitsilano has been made to rhyme with Capilano. (12th Report of the Okanagan Historical Society, 1948, citing BCHQ, 2:67).

Source: included with note

Alexander Ross in his account of his visit to the Kamloops area in 1812 mention returning to Fort Okanagan by way of the "Samilkameigh River," and he lists the "Samilkameigh" as one of the twelve Indian tribes making up the Okanagan nation. Sir George Simpson in his Columbia journal of 1825 mentions the "Samilkumeighs" as living on the north side of the river of the same name. "Samilkameigh" became corrupted into "Similkameen" by analogy with its tributary the Tulameen River.

Source: Canadian Geographical Names Database, Ottawa