The Upper Canada Rebellion was, along with the Lower Canada Rebellion in Lower Canada, a rebellion against the British colonial government in 1837 and 1838. Collectively they are also known as the Rebellions of 1837.
As it had before the War of 1812, the government of Upper Canada continued to fear what it suspected might be a growing interest in American republicanism within the province. Reasons for this must be sought in the patterns of settlement across the province in the last half-century. Although the British had originally hoped that an orderly settlement in Upper Canada would inspire the former American colonies to abandon their democratic form of government, demographic realities intervened. After an initial group of about 7,000 United Empire Loyalists were thinly settled across the province in the mid-1780s, a far larger number of American settlers came after the American Revolution were attracted by the cheap land grants offered by Lieutenant-Governor John Graves Simcoe to promote land settlement. Although these settlers, known as "late-Loyalists," were required to take an oath of allegiance to the British Crown in order to obtain land, their fundamental political allegiances were always considered dubious. By 1812 this had become acutely problematic since the American settlers outnumbered the original Loyalists by more than ten to one. It was this reality that led American legislators to speculate that bringing Upper Canada into the American fold would be a "mere matter of marching." After the War of 1812 the government took active steps to prevent Americans from taking an oath of allegiance thereby making them ineligible to obtain land grants. Relations between the appointed Legislative Council and the elected Legislative Assembly, moreover, became increasingly strained in the years after the war over issues of both immigration and taxation.
Meanwhile, a group of rebels from the settlement of London (in the west of Upper Canada), led by Charles Duncombe, marched toward Toronto to support Mackenzie. Colonel Allan MacNab met them near Hamilton, Ontario on December 13, and the rebels fled.
The victorious Tory supporters burned homes and farms of the known rebels and suspected supporters. In the 1860s, some of the former rebels were compensated by the Canadian government for their lost property in the rebellion aftermath.
Mackenzie, Duncombe, John Rolph and 200 supporters fled to Navy Island in the Niagara River, where they declared themselves the Republic of Canada on December 13. They obtained supplies from supporters in the United States resulting in British reprisals (see Caroline Affair). On January 13 1838, under attack by British armaments, the rebels fled. Mackenzie went to the United States where he was arrested and charged under the Neutrality Act The other major leaders, Van Egmond, Samuel Lount, and Peter Matthews were arrested by the British; Van Egmond died in prison, and Lount and Matthews were executed at 8 AM on April 12, 1838 in Toronto. Their last words were: "Mr. Jarvis, do your duty; we are prepared to meet death and our Judge."
The rebels continued their raids into Canada, however, using the U.S. as a base of operations and cooperating with the U.S. Hunter Lodges, dedicated to the overthrow of British rule in Canada. The raids did not end until the rebels and Hunters were decisively defeated at the Battle of the Windmill, nearly a year after the initial battle at Montgomery's Tavern.
Compared to the Lower Canada Rebellion, the initial portion of the Upper Canada Rebellion was short and disorganized. However, the government in London, England was very concerned about the rebellion, especially in light of the strong popular support for the rebels in the United States and the more serious crisis in Lower Canada. Bond Head was recalled in late 1837 and replaced with Sir George Arthur who arrived in Toronto in March 1838 and sent Lord Durham, who was assigned to report on the grievances among the colonists and find a way to appease them. His report eventually led to greater autonomy in the Canadian colonies, and the union of Upper and Lower Canada into the Province of Canada in 1840.
A few of the rebels were hanged or transported, but most were pardoned. A general pardon (for everyone but Mackenzie) was issued in 1845, and Mackenzie himself was pardoned in 1849 and allowed to return to Canada, where he resumed his political career. Mackenzie was strongly disillusioned after his time in the United States, writing to his son that "after what I have seen here, I frankly confess to you that, had I passed nine years in the United States before, instead of after, the outbreak, I am sure I would have been the last man in America to be engaged in it" (Charles Lindsey, The Life and Times of William Lyon Mackenzie and the Rebellion of 1837–38. 1862; cited by Betsy Dewar Boyce, The Rebels of Hastings, 1992).