Historical federal electoral districts of Canada
This is a list of past arrangements of Canada's electoral districts. Each district sends one member to the House of Commons of Canada. In 1999 and 2003, the Legislative Assembly of Ontario was elected using the same districts within that province. 96 of Ontario's 107 provincial electoral districts, roughly those outside Northern Ontario, remain coterminous with their federal counterparts.
Federal electoral districts in Canada are re-adjusted every ten years based on the Canadian census and proscribed by various constitutional seat guarantees, including the use of a Grandfather clause, for Quebec, the Central Prairies and the Maritime provinces, with the essential proportions between the remaining provinces being "locked" no matter any further changes in relative population as have already occurred. Any major changes to the status quo, if proposed, would require constitutional amendments approved by seven out of ten provinces with two-thirds of the population to ratify constitutional changes allowing changes in the existing imbalance of seats between various provinces. During the 2012 federal electoral redistribution, an attempt was made to get around this by adding additional seats. These 30 new seats are the largest increase in the number of seats at any single redistribution since confederation.