The federal Liberal Party has been in existence since Confederation in 1867. However, they were a relatively minor factor in Canadian politics for the remainder of the 19th century.
The Liberals opposed the Conservatives on two key issues. The Liberals, in their early years, supported free trade. They were also less supportive of close ties with the United Kingdom than were the Conservatives.
There were many Liberal prime ministers in the 20th century, but two stand out above all of the others: William Lyon Mackenzie King and Pierre Elliott Trudeau. Between them, King and Trudeau had a combined 45 years as Liberal leader, and 36 years as prime minister.
King and Trudeau both played leading roles in the moves toward greater formal independence from Britain that I described here. King was prime minister during the negotiations that led up to the 1931 decision by the U.K. Parliament to grant Canada and other former colonies control over their routine legislation. However, Richard Bennett, a Conservative, had become prime minister before that decision was finalized.
Trudeau engineered the process of developing a Canadian constitution that would no longer be controlled by the British Parliament. That process reached fruition in 1982, two years before Trudeau retired as prime minister.
Jean Chretien, a Liberal, served as prime minister from 1993 to 2003. He was aided by the split in the conservative vote between the Progressive Conservatives and the Canadian Alliance that I described here.
Two developments in the current decade combined to remove the Liberals from power at the federal level. Their opposition on the right was no longer divided, after the Progressive Conservatives and the Canadian Alliance merged in 2003. And there was a corruption scandal related to funds that were appropriated for a public relations campaign in opposition to Quebec independence.
The Liberals' current leader, Stephane Dion, has been in that position since 2006.