Chilliwack River adopted in the 18th Report of the Geographic Board of Canada, 31 March 1924. Application altered 6 February 1948, when damming operations around Chilliwack separated the watercourse into 2 separate streams. The upper portion of the original watercourse (still called Chilliwack River) was diverted southward and now flows into the Vedder River; the lower portion - still flowing northwest through Chilliwack into the Fraser River but carrying much less water now - was renamed Chilliwack Creek. See Chilliwack (City) for origin information.
Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office