the north bank of the Saskatchewan River, and Strathcona, on the south bank of the river, developed separately - economically, politically, and socially - because travel and communication across the river were limited. (They merged in 1912.) In addition to affording an outlet for civic rivalries, the games between the Edmonton Thistle and Strathcona Shamrock hockey clubs united individuals from different social classes and diverse cultural backgrounds in support of their team. Skiing began in Banff in the 1890s and received its main impetus with the winter carnival in 1916. In the next decades the carnival became popular; ski jumping and cross-country races led to much publicity. By 1940, Banff had become one of Canada's leading skiing centres, and was heavily promoted as a vacation destination by the Canadian Pacific railway. Oil, gas and oil sands Alberta has played the central role in Canada's petroleum industry —both from the discovery and development of conventional oil and natural gas, and through the development of the world's foremost bitumen deposits in the province's vast northern oil sands. The province became one of the world's foremost producers of crude oil and natural gas, generating billions of revenue for the province and igniting a bitter feud with the national government. The first oil field in western Canada was Turner Valley, south of Calgary, where large supplies were discovered at a depth of about . Calgary became the oil capital, with a reputation for swashbuckling entrepreneurship. Turner Valley was for a time the largest oil and gas producer in the British Empire. Three distinct phases of discovery marked the field's history and involved such Albertans as William Stewart Herron and A. W. Dingman, and companies that included Calgary Petroleum Products, later the Royalite Oil Company; Turner Valley Royalties; and later the Home Oil Company. In 1931, the province enacted the Oil and Gas Wells Act to reduce the heavy waste of natural gas. In 1938, the Alberta Petroleum and Natural Gas Conservation Board was successfully established and enacted conservation and prorating measures. The goal was to maximize the long-term yield, as well as to protect small producers. In 1947 an even bigger field opened at Leduc, south of Edmonton, and in 1948 oil mining began at Redwater. Both these fields were overshadowed in importance in 1956 with the discovery of the Pembina field west of Edmonton. Other fields were discovered east of Grande Prairie and