William Lyon Mackenzie King was Canada's longest-serving prime minister (1921-26; 1926-30; 1935-48). When Mackenzie King succeeded Sir Wilfrid Laurier as leader of the Liberal Party in 1919, the most significant threat to national unity came from the prairie west. King set off to rebuild Liberal support in the frustrated region by supporting the prairie position on such critical issues as tariffs, freight rates, natural resources, railways, and immigration. He lured former Liberal-Progressives back into party ranks, made sure to offer federal Cabinet posts to influential leaders, and sought to form strong relationships with the provincial governments of Alberta, Manitoba, and most specifically the ardently Liberal province of Saskatchewan under Premiers Charles Dunning and Jimmy Gardiner. Both Premiers ended up as influential Ministers in King's federal Cabinets. Part of King's strategy in rebuilding Liberal fortunes in the west included representing a Saskatchewan constituency. After being defeated in the 1925 general election in the Ontario riding of North York, King was elected to represent the federal constituency of Prince Albert in a by-election on February 15, 1926. King held the Saskatchewan constituency for the majority of his career and was instrumental in the creation of the Prince Albert National Park in 1926. He was defeated in the riding in the general election of June 11, 1945, and held the seat of Glengarry, Ontario, for the remaining three years of his career.
Robert Wardhaugh