From its introduction in 1961 to its end in September 1973, the National Oil Policy (NOP) was the cornerstone of Canadian energy policy. It "established a protected market for domestic oil west of the Ottawa Valley, which freed the industry from foreign competition," and the five eastern provinces, which included major refineries in Ontario and Quebec, continued to rely on foreign imports of crude oil, such as from Venezuela. In 1973, "the federal government announced the extension of the inter-provincial oil pipeline to Montreal (completed in 1976), froze prices of domestic crude and certain oil products, and sought to control export prices. The federal government announced this change in policy so that supply problems in the United States would not automatically raise prices for Canadian consumers."