William Lyon Mackenzie King (1874-1950) was prime minister of Canada for more than 21 years, a longer period in office than any other first minister in the history of countries in the British Commonwealth.

On Dec. 17, 1874, W. L. Mackenzie King was born at Berlin (later Kitchener), Ontario. His father, John King, was a lawyer, and his mother, Isabel Mackenzie King, was the daughter of William Lyon Mackenzie, leader of the short-lived rebellion of 1837 in Upper Canada. His maternal spiritual inheritance was of some significance to King and may help to explain his lifelong ambivalence between his urge to be a reformer and his craving for social respectability.

King graduated from the University of Toronto in 1895, undertook postgraduate studies at Chicago, and secured a doctorate in political economy from Harvard. In Chicago he was associated with Jane Addams's work at Hull House, an experience which strengthened his interest in social...