The City of Cornwall owns a rich and diverse history and is one of Ontario's oldest permanent settlements. Originally named New Johnstown, the name was changed to Cornwall in honor of Prince George, the Duke of Cornwall.

The city was later incorporated as a town in 1834 and became a city in 1945. Cornwall was first settled in 1784 by a group of disbanded soldiers and refugees from the United Empire Loyalists of the First Battalion King's Royal Regiment of New York and a contingent of the 84th Royal Highland Emigrants.

For years, these Loyalists had fought on behalf of Britain in Northern New York and Vermont during the American Revolutionary War. These people came to settle and prosper on the lands, which the Crown had granted them in reward for their loyal service during the war.

Cornwall served as a garrison town, as well as a communications and supply post during the War of 1812. At nearby Crysler's farm, the Loyalists successfully repelled American troops in one of the most famous battles of the War.

Under the influence of schoolmaster John Strachan, Cornwall was transformed into a unique center of learning and political influence that served as training ground for the "Family Compact", Ontario's ruling class until the 1850's.

During the latter half of the 19th century, the town emerged as an important industrial center in Eastern Ontario. The early growth can be attributed to many of the same factors that continue to attract manufacturers to modern-day Cornwall:

• Unlimited waterpower
• A major market
• Montreal
• Was in close proximity
• And a labor force was at hand.

Construction of the Cornwall Canal between 1834-42 provided transportation and water power for the numerous mills and textile plants which located along the waterfront.

Industrial sites were first laid out in the mid 1840's, and soon flour mills, tanneries, and woolen mills were in operation. Among the first major manufacturers to locate in Cornwall were the Stormont, Dundas Canada Cotton Mills.

The town’s population doubled from 2,033 in 1871 to 4,468 in 1881, due to the industrial expansion that happened on the waterfront. A major industry which still provides a significant influence on the City's economy was built during this period, namely, the Toronto Paper Company, which now operates as a division of Domtar Specialty Fine Papers Inc.

Another period of staggering growth took place between 1921 and 1931, when Cornwall's population increased by fifty percent. A highlight from this era was the establishment of Courtaulds Canada Inc.'s rayon manufacturing mill. In addition, Canadian Industries Limited (C.I.L.), now I.C.I. Canada Inc., has operated a large plant in Cornwall since 1935.

Cornwall's steady growth was capped in the 1950's with the building of the St. Lawrence Seaway. Construction of the Seaway began on August 10, 1954 and was finalized on Dominion Day, July 1, 1958.

Thousands of spectators watched as thirty tons of dynamite were detonated causing the last coffer dam to flood the riverbed and Lake St. Lawrence. This historic event marked the largest international hydro-electric power dam.