Mitlenatch Island Park was established by Order in Council 1842, 14 July 1961. Foreshore added per OIC 559, 22 February 1966. Name changed Mitlenatch Island Nature Park per OIC 1201/90. Conversion of OIC to Statute designation per Bill 17-2000: Protected Areas of British Columbia Act, 29 June 2000; the whole containing 155 hectares (36 hectares of upland and 119 hectares of foreshore) more or less.
Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office