The Province of Quebec was established by Great Britain in 1763. It was smaller than the present province-except for a part extending into Labrador, it was bounded on the north by a line between Lakes Nipissing and St. John. On the south, the boundary ran eastward from the northern tip of Lake Huron to New England. By the Quebec Act of 1774, Great Britain vastly expanded Quebec by including in it all land in North America between the Appalachians and the Mississippi River to the Ohio River.

By the peace treaty that followed the American Revolution, Great Britain ceded to the United States the land in the province of Quebec below the St. Lawrence and the Great Lakes. During and after the Revolution, the upper (or western) part of the province began to be settled by English-speaking persons. Many of these settlers were from colonies that became the United States. They had opposed the revolution and were called Loyalists. To give them a separate government, the British Parliament adopted the Constitutional Act of 1791. This act divided the province into Upper Canada (what is now southern Ontario) and Lower Canada.