Control of all of Canada passed from France to Great Britain in 1763 when the Treaty of Paris ended the Seven Years' War in America. The territories of modern southern Ontario and southern Quebec were initially maintained as the single Province of Quebec, as it had been under the French. From 1763 to 1791, the Province of Quebec maintained its French language, cultural behavioural expectations, practices and laws. This status was renewed and reinforced by the Quebec Act of 1774, which expanded Quebec's territory to include part of the Indian Reserve to the west (i.e., parts of southern Ontario), and other western territories south of the Great Lakes including much of what would become the United States' Northwest Territory, including the modern states: Illinois, Indiana, Michigan, Ohio, Wisconsin and parts of Minnesota.
The part of the province west of Montreal and Quebec in the upper river basin soon began receiving many English-speaking Protestant United Empire Loyalists who arrived in the area as refugees from the American Revolution. This region quickly became culturally distinct. While the act addressed some religious issues, it did not appease those used to English law.
"Upper Canada" became a political entity on December 26, 1791 with the Parliament of Great Britain's passage of the Constitutional Act of 1791. The act divided the Province of Quebec into Upper and Lower Canada. The division was effected so that Loyalist American settlers and British immigrants in Upper Canada could have English laws and institutions, and the French-speaking population of Lower Canada could maintain French civil law and the Catholic religion.
The first lieutenant-governor was John Graves Simcoe. On February 1, 1796, the capital of Upper Canada was moved from Newark (now Niagara-on-the-Lake) to York (now Toronto), which was judged to be less vulnerable to attack by the Americans.
Read more about this topic: Upper Canada