1966, Tottenham-Smith stepped down as president. The board appointed Derek Fenton Mitchell (1918–1981) as his replacement. The company's first offices were established at 550 Sherbrooke Street West. In 1962 it relocated to the new Standard Life Building at 1245 Sherbrooke Street West. BP Canada made its largest purchase to date in 1964, when it acquired the refining and marketing assets of Canada-Cities Service Limited for $50 million. The purchase included 750 gas stations, 75 bulk plants, and the Oakville Refinery, which had been built in 1958. Integrated major, 1969–1982 In 1969 Towers retired as chairman and the board elected Robert MacLaren Fowler (1906–1980) as his replacement. That same year, the company underwent a restructuring. The holding company, the British Petroleum Company of Canada Limited, was renamed BP Canada (1969) Limited. The marketing arm, BP Canada Limited, was renamed BP Oil Limited, and BP Refinery Canada Limited was placed under it as a subsidiary. Triad Oil Company, of which BP Canada now had a 65.9 percent stake, was renamed BP Oil and Gas Limited. The August 1969 discovery of the Prudhoe Bay Oil Field inspired British Petroleum to increase its investments in North America. In August 1971, BP Canada made an offer to purchase Supertest Petroleum. To undertake the acquisition, BP Canada Limited (the holding company) exchanged all shares of its subsidiary companies for an 83.7 percent stake in Supertest, which was held by Corlon Investments Limited. Supertest was then renamed BP Canada Limited, while the holding company became BP Canadian Holdings Limited. BP Holdings then increased its stake in BP Canada (or Supertest) to 97.8 percent at a share price of $16.50. In 1970, BP Canada held rights to 26.7 million acres, up from 19.3 the previous year. Its recent growth included significant holdings in the arctic. In 1971, the company drilled wells on Prince Patrick Island and Graham Island as part of the Panarctic Oils consortium. In 1972, oil and gas production was 22,132 barrels-per-day, up from 18,582 the previous year. The 1973 oil crisis instigated by OPEC created havoc in global oil markets, however, in 1974 BP Canada increased its profits by 82 percent. In 1975 the company completed a 40,000 barrels-per-day expansion of the Oakville Refinery and completed the takeover of British Columbia Oil Sands Limited. That same year, the company sold 1,200 of its 3,000 retail outlets in Ontario and Quebec. Also in 1975, BP Canada