What was the Act of Union of 1840?

The Act of Union of 1840 (3 and 4 Victoria, c. 35) was a British statute that merged the colonies of Upper Canada and Lower Canada into a single Province of Canada with a single legislature. The Act received royal assent on July 23, 1840 and came into force on February 10, 1841. It was based directly on the recommendations of Lord Durham's Report of January 1839, which had advocated union as a means of assimilating French Canadians into a British majority. The Act of Union remained in force until Confederation on July 1, 1867.

The unified Province of Canada had two regional sub-units: Canada West (the former Upper Canada, today's southern Ontario) and Canada East (the former Lower Canada, today's southern Quebec). The Province had a single Legislative Assembly with equal representation: 42 members each from Canada West and Canada East, totalling 84 members. This equal representation, called the 'double majority' principle in practice, was an assimilationist device. In 1841 Canada East had a larger population than Canada West (about 670,000 versus 480,000); by the 1850s Canada West's population exceeded Canada East's, and Canada West Reformers began demanding representation by population (Rep by Pop). Canada East's lower share of seats per capita was a structural defence against the British majority's ambition.

The Act made English the sole official language of the legislature and government records. This provision (section XLI) was repealed in 1848 after Reformer political mobilisation; from January 18, 1849 the legislature recognised both English and French. The legislature met successively at Kingston (1841 to 1843), Montreal (1844 to 1849, until the Parliament Buildings were burned by an Anglo-Tory mob during the Rebellion Losses Bill controversy of April 1849), Toronto (1850 to 1851, 1855 to 1859), Quebec City (1852 to 1855, 1859 to 1865), and finally Ottawa (from 1866).

The Act of Union proved unstable politically. The double majority principle led to repeated political deadlock between French and English Canadian majorities. Between 1841 and 1867 the Province had 26 different governments, an average of one every year. Robert Baldwin and Louis-Hippolyte La Fontaine led the Reform alliance that secured responsible government in March 1848 (the first responsible ministry was the Baldwin-La Fontaine ministry). The political deadlock contributed directly to the Great Coalition of June 1864 (uniting Conservatives under John A. Macdonald, Reformers under George Brown, and Bleus under George-Étienne Cartier) and to Confederation. The Act of Union was effectively repealed by the British North America Act of 1867, which created modern Ontario and Quebec as separate provinces of the new Dominion of Canada.