Châteauguay is an off-island suburb of Montreal, in southwestern Quebec, located both on the Chateauguay River and Lac St-Louis, which is a section of the St. Lawrence River. The population of the city of Châteauguay at the 2011 Census was 45,904, and the population centre was 70,812.
The land was first given to Charles Lemoyne by the governor of New France at the time, the Comte de Frontenac with the intention of setting up a seigneurie in the area. Afterwards the seigneurie was assumed by Zacharie Robutel de la Noue in 1706. In 1763 France relinquished its claims in Canada and Châteauguay was now under British mandate. The seigneurie was bought by Marguerite d'Youville, a founder of the Quebec religious society the Grey Nuns in 1765 and 10 years later construction began on the Church of Saint-Joachim.
Châteauguay played an important part in the colonial history of North America. With the United States having declared war on Britain in 1812, Châteauguay was seen as little more than a good vantage point to post troops to defend Montreal against an invasion. This prong of the American advance on Montreal ended with the Battle of the Châteauguay, where on October 26, 1813, Lieutenant Colonel Charles de Salaberry succeeded in halting the American force of 4,000 advancing on Montreal with only some 400 troops, mostly French-Canadian and 170 Kahnawake Mohawk warriors. The second American incursion towards Montreal was defeated shortly after at Crysler's Farm on November 11.