Using a new measure of urbanity for every federal electoral district in Canada from 1896 to the present, this article describes the long-term development of the urban-rural divide in Canadian federal elections. We focus on three questions: (1) when the urban-rural divide has existed in Canada, identifying three main periods—the 1920s, the 1960s and 1993–present—in which the urban-rural cleavage has been especially important in federal elections; (2) where the urban-rural divide has existed, finding that in the postwar period the urban-rural cleavage is a pan-Canadian phenomenon; and (3) how well urbanity predicts district-level election outcomes. We argue that the urban-rural divide is important for understanding election outcomes during several periods of Canadian political development, and never more so than in recent decades. We conclude by discussing the implications of our findings for research on urban-rural cleavages, Canadian electoral politics and Canadian political development.