Great Canadian Oil Sands

Great Canadian Oil Sands Limited was a Canadian heavy oil company that existed between 1953 and 1979. In 1962, GCOS received a permit from the Alberta government to build a 31,500 barrels-per-day synthetic crude plant in the Athabasca oil sands. The following year, Sun Oil acquired an 83 percent stake in the company and in 1964 construction of the plant began. When GCOS opened its plant on 30 September 1967, it became the first company in the world to produce heavy oil commercially. In 1979, Sun merged its Canadian subsidiary, the Sun Oil Company, with GCOS to form Suncor.