The situation changed dramatically in 1947, when Imperial Oil drilled a well near Leduc, Alberta, to see what was causing peculiar anomalies on its newly introduced reflection seismology surveys. The peculiar anomalies turned out to be oil fields, and Leduc No. 1 was the discovery well for the first of many large oil fields. As a consequence of the large finds, cheap and plentiful Alberta oil produced a huge surplus of oil on the Canadian Prairies, which had no immediate market since the major oil markets were in Ontario and Quebec. In 1949, Imperial Oil applied to the federal government to build the Interprovincial Pipeline (IPL) to Lake Superior, which allowed it to supply the Midwestern United States. By 1956, the pipeline had been extended via Sarnia, Ontario, to Toronto; at , it became the longest oil pipeline in the world. The federal government gave approval to build a pipeline in Western Canada, and in 1953, the Transmountain Pipeline was built from Edmonton to Vancouver, British Columbia, with an extension to northwest Washington. The pipelines did more to improve the energy security of the United States than that of Canada since the Canadian government was more interested in Canada's trade balance than in military or energy security. The Canadian government assumed that Eastern Canada could always import enough oil to meet its needs and that imported oil would always be cheaper than domestic oil.