How did the American Revolution lead to Loyalist settlement in Ontario?

The American Revolution was a pivotal event that fundamentally shaped the population and political structure of what is now Ontario. Following the conflict, approximately 10,000 United Empire Loyalists—colonists who remained loyal to the British Crown—fled the new United States to seek refuge in British North America.1

Many of these refugees, primarily from upper New York and Pennsylvania, crossed the frontier and settled along the St. Lawrence River west of existing French settlements. This influx of English-speaking Protestants transformed the region's demographic character. Because these settlers desired land ownership under British law and representative government—rights not fully provided under the Quebec Act—their presence prompted significant political change.23

In response, the British government passed the Constitutional Act of 1791, which divided the colony of Quebec into two parts: a French-majority province known as Lower Canada and a loyalist-dominated province called Upper Canada, the precursor to modern Ontario. This new province was established with its own representative government, setting the foundation for the region's future development.21