The long period of Liberal domination in Parliament ended in 1957. The St. Laurent government was replaced when the Progressive Conservatives (called Conservatives before 1942) took office under the prime ministership of John G. Diefenbaker.

In the 1962 elections the Progressive Conservatives lost their control of Parliament, but no other party was able to win a majority. Diefenbaker, as leader of the largest minority party, formed a weak coalition government. In February 1963 his government fell on the issue of Canada's failure to execute its 1958 commitments to accept nuclear weapons from the United States for the joint defense of North America.

In general elections on April 8 the Liberals won more seats than any other party, and Liberal leader Lester B. Pearson was named prime minister of Canada in 1963 at the head of another minority government . In 1968 the Liberals chose Pierre Elliott Trudeau to succeed him. In the general elections in June, Trudeau won, with the Liberals taking a majority. This was the first election to use the electoral constituency boundaries of 1965.

In the October 1972 elections Trudeau's Liberals won but failed to gain a majority. They were able to stay in power with New Democratic support, but in May 1974 Trudeau's government fell. The Liberals won a new majority in the July parliamentary elections.

Economic issues brought about the Liberals' defeat five years later. The Progressive Conservatives, led by Joe Clark, formed a minority government that fell after only six months. Although Trudeau resigned his party leadership in November 1979, he was again named prime minister in 1980.

Trudeau resigned once again in 1984 and was succeeded by John Turner on June 30. On July 9, Turner called for dissolving Parliament and holding a new election. He retained ministers from the Trudeau Cabinet and appointed Trudeau supporters to the Senate, courts, and diplomatic posts.

Dissatisfaction with this continuation of Trudeau's influence led to victory in the September election for the Progressive Conservatives, under the leadership of Brian Mulroney. Mulroney sought to improve relations with the United States.

In October 1987 Canada and the United States reached agreement on a trade pact to eliminate all bilateral tariffs over a ten-year period beginning Jan. 1, 1989. The two countries signed a Great Lakes water-quality agreement in November. Both countries agreed to track and clean up sources of pollution.

In January 1988 abortion was legalized in Canada. Victories by Mulroney and his Conservative party in the November 1988 elections guaranteed passage of the free-trade agreement.

The socialist New Democratic party chose Audrey McLaughlin, the member of Parliament from the Yukon, as its leader in 1989--the first woman to head a major Canadian political party. While the international political climate became more conservative, the party began to dominate Canadian leadership in the early 1990s. New Democrats were elected premiers of the provinces of Ontario, Saskatchewan, and British Columbia.

With his popularity slumping, Mulroney resigned in February 1993. He was succeeded by Kim Campbell, who became the first female prime minister in Canadian history. Campbell and the Conservatives were annihilated in the October 1993 elections, retaining only two seats in the House of Commons. The Liberal party won 177 seats to take control of the government, and Jean Chretien became prime minister.