Cornwall is a city in Eastern Ontario, Canada and the seat of the United Counties of Stormont, Dundas and Glengarry, Ontario. Cornwall is Ontario’s easternmost city, located on the St. Lawrence River, Quebec City-Windsor Corridor  and Highway 401, and is the urban centre for surrounding communities, which include Long Sault and Ingleside to the west, Mohawk  Territory of Akwesasne to the south, St. Andrew’s and Avonmore to the north, and Glen Walter, Martintown, Williamstown, and Lancaster to the east.

Cornwall is located in Eastern Ontario approximately 100 kilometres (60 mi) southeast of Ottawa, Canada’s capital, 100 kilometres (60 mi) southwest of Montreal, Quebec’s largest city, and 400 kilometres (250 mi) northeast of Toronto, Ontario’s capital. It is named after the English county of Cornwall which is represented in the flag and coat of arms which both boast the duchy standard.

Aboriginal peoples have lived in and around the area of present day Cornwall for millennia.

The first serious European settlement was established in 1784, by United Empire Loyalists, primarily from New York. They were led by Lieutenant-Colonel Sir John Johnson and were soldiers from the First Battalion King’s Royal Regiment of New York and a contingent of the 84th Royal Highland Emigrants. Following the success of rebellious colonists in the American Revolution, the United Empire Loyalists (as they were later called) migrated to Canada. The British government helped them settle there in reward for their loyalty and compensation for their losses in the United States.

They founded a settlement on the site formerly called Pointe Maligne by French colonists. They renamed it New Johnstown. Later renamed Cornwall for the Duke of Cornwall, Prince George, the town in 1834 became one of the first incorporated municipalities in the British colony of Upper Canada.

West of Cornwall, along the St. Lawrence River, were several smaller communities. Now known as the Lost Villages, the communities were permanently flooded in 1958 by the construction of the St. Lawrence Seaway. The massive Moses-Saunders hydroelectric dam at the western end of the city required a reservoir, and the villages were flooded when it was filled.