John Lambton, 1st Earl of Durham in the context of Canada West

The Province of Canada (or the United Province of Canada or the United Canadas) was a British colony in British North America from 1841 to 1867. Its formation reflected recommendations made by John Lambton, 1st Earl of Durham, in the Report on the Affairs of British North America following the Rebellions of 1837–1838.

The Act of Union 1840, passed on 23 July 1840 by the British Parliament and proclaimed by the Crown on 10 February 1841, merged the Colonies of Upper Canada and Lower Canada by abolishing their separate parliaments and replacing them with a single one with two houses, a Legislative Council as the upper chamber and the Legislative Assembly as the lower chamber. In the aftermath of the Rebellions of 1837–1838, unification of the two Canadas was driven by two factors. Firstly, Upper Canada was near bankruptcy because it lacked stable tax revenues, and needed the resources of the more populous Lower Canada to fund its internal transportation improvements. Secondly, unification was an attempt to swamp the French vote by giving each of the former provinces the same number of parliamentary seats, despite the larger population of Lower Canada.

The Report on the Affairs of British North America, (French: Rapport sur les affaires de l’Amérique du Nord britannique, 1839) commonly known as the Durham Report or Lord Durham's Report, is an important document in the history of Quebec, Ontario, Canada and the British Empire. It called for reforms that sought to address concerns expressed during the rebellions of 1837–38.

The Report was written by the notable British Whig politician John Lambton, 1st Earl of Durham, who was sent to the Canadas in 1838 to investigate and report on the causes of the rebellions of 1837–38. He had just been appointed Governor General and given special powers as high commissioner of British North America.

The Rebellions of 1837–1838 (French: Rébellions de 1837) were two armed uprisings that took place in Lower and Upper Canada in 1837 and 1838. Both rebellions were motivated by frustrations with lack of political reform. A key shared goal was responsible government, which was eventually achieved in the incidents' aftermath. The rebellions led directly to Lord Durham's Report on the Affairs of British North America and to the Act of Union 1840 which joined the two colonies of the Canadas into a single colony. The report and subsequent developments eventually led to the Constitution Act, 1867, which created the contemporary country of Canada and its government.

The Canadas is the collective name for the provinces of Lower Canada and Upper Canada, two historical British colonies in present-day Canada. The two colonies were formed in 1791, when the British Parliament passed the Constitutional Act, splitting the colonial Province of Quebec into two separate colonies. The Ottawa River formed the border between Lower and Upper Canada.

The Canadas were merged into a single entity in 1841, shortly after Lord Durham published his Report on the Affairs of British North America. His report held several recommendations, most notably union of the Canadas. Acting on his recommendation, the British Parliament passed the Act of Union 1840, which went into effect in 1841, uniting the Canadas into the Province of Canada.