Sainte-Julie, is an off-island suburb of Montreal, in southwestern Quebec, Canada, east of Montreal in Marguerite-D'Youville Regional County …Sainte-Julie, is an off-island suburb of Montreal, in southwestern Quebec, Canada, east of Montreal in Marguerite-D'Youville Regional County Municipality. The population as of the Canada 2021 Census was 30,045. In 2009 Sainte-Julie was called one of the best towns in which to live in Quebec, and the city is often known as "The Happiest City in Quebec".