The abortive rebellions dramatized the need to reform Canada’s outmoded and constrictive constitution, prompting the “Canadian question” to become a leading issue in British politics. Whig reformer John George Lambton, 1st earl of Durham, was appointed governor-general to inquire into the causes of the troubles. Durham’s stay in Canada was brief, but his inquiry was sweeping and his recommendations trenchant. Durham perceived that the colonies had stagnated and that, if they were to live side by side with the dynamic United States, they must be brought into the full stream of material progress. One political means to achieve this goal was union. Durham decided the time for the union of all the North American colonies had not yet come, but he did recommend the reunion of at least the two Canadas in order to realize the economic possibilities of the St. Lawrence River valley. In Durham’s view, union would also hasten the assimilation of the French, whom he viewed as a backward people. He also adopted a proposal of certain Upper Canadian and Nova Scotian reformers for “responsible government,” which would make the colonial executive responsible to the assembly and assure colonial self-government.

The British government refused an explicit grant of responsible government but did accept the proposal to unite the Canadas. In 1841 the united Province of Canada was established under a new and dynamic governor, Charles Poulett Thomson (later Lord Sydenham). Although the French of Lower Canada (now renamed Canada East) outnumbered the English of Upper Canada (Canada West), both sections received an equal number of seats in the new legislature. The British intended that this policy would facilitate assimilation of the French, but the French, led by such astute reform leaders as Louis Hippolyte LaFontaine, took advantage of divisions among the English-speaking legislators by allying themselves with the reformers from Canada West to push for responsible government and to make themselves indispensable for governmental stability. In Britain the success of the Industrial Revolution led to the growth of free-trade liberalism and a desire to dismantle the colonial empire. The last major protective British tariffs (the Corn Laws) were repealed in 1846, and some time after that colonial governors were instructed to implement a policy of responsible government. The policy received its first real test in 1849, when the reform ministry headed by LaFontaine and Robert Baldwin of Canada West passed a law to compensate victims of the 1837 rebellions. Governor General James Bruce, 8th earl of Elgin, Lord Durham’s son-in-law, signed the law despite strong opposition from conservatives. In reaction a mob burned the parliament buildings in Montreal.

The British North American colonies achieved self-government by 1855, and their laws and institutions were remodeled to fit the individual needs of each colony. By midcentury, Canada was poised for expansion. The British repeal of the Corn Laws had deprived the colonies of imperial protective tariffs. Some fearful merchants favoured American annexation, but to no avail. In an attempt to draw the trade of the American Midwest down the St. Lawrence River valley, work was begun on the Grand Trunk Railway in 1853. The Reciprocity Treaty (1854) between Canada and the United States eliminated customs tariffs between the two, and the resulting increase in trade with the United States—which in part replaced trade with the United Kingdom—led to an economic boom in Canada. Economic growth was especially stimulated after 1861 by the American Civil War. When the U.S. government gave notice in 1864 that it wished to abrogate the treaty by 1865, colonial politicians promoted the unification of the British North American colonies to provide a substitute market. This move was also made necessary by a continuing political deadlock between conservatives and reformers in Canada, by growing fears of U.S. military power, and by a desire to annex the northwest. After the merger of the North West Company and the Hudson’s Bay Company in 1821, direct links between Canada and the west had been cut. In Canada West, however, a shortage of good agricultural land was forcing young men to leave for the United States to homestead, and demands grew to annex the northwest to provide room for expansion.

The first significant step toward union, later called confederation, was the formation of the Great Coalition, a government that united George Brown of Canada West—leader of the so-called Clear Grits reform movement—with the Liberal-Conservatives’ John A. Macdonald of Canada West and George Étienne Cartier of Canada East. In September 1864 the three leaders attended a conference at Charlottetown, Prince Edward Island, in which Maritime political leaders discussed Maritime union. They persuaded the Maritimes to postpone such a union and instead to discuss creating a union of all of British North America. On October 10, 1864, an agreement to establish a general federal union was reached in Quebec. The agreement was immediately approved by the British government, which was eager to allow the colonies to govern themselves and to be rid of its obligation to defend them inland from Quebec. The path to union was not without obstacles. New Brunswick voted against union in 1865, then reversed itself in 1866; Prince Edward Island refused to enter until 1873; Newfoundland (including Labrador) also refused and did not join Canada until 1949. But the Canadas and the British government applied quiet but strong pressure on the reluctant colonies. In 1867 the three colonies of Nova Scotia, New Brunswick, and the Canadas were united as four provinces (Nova Scotia, New Brunswick, Quebec, and Ontario) of the Dominion of Canada under the British North America Act, which, with certain amendments, served as the “constitution” of Canada until the adoption of the Canada Act (also known as the Constitution Act) in 1982.

The British North America Act—later retitled the Constitution Act, 1867—provided constitutions, based on the British model, for the new provinces of Quebec and Ontario, confirmed the language and legal rights of the French, and divided power between the federal government and the provinces. At its origin the union was not truly federal, as the central government was given broad powers, not unlike those the British government had possessed over the colonies. Over time, however, judicial interpretation and the growth of provincial rights moved the country toward a more federal system. For the moment, a strong central government was deemed necessary in order to develop the northwest and to build a railway to the Pacific that would bind the vast new territories there to the original provinces.