Deux-Montagnes’ first name was Saint-Eustache-du-Lac. When it was officially founded on August 18, 1921, this municipality’s population totalled less than 300 permanent residents. Today’s Grand-Moulin District, which would much later be called Deux-Montagnes, is the area where these first inhabitants chose to elect residence.
The City of Deux-Montagnes was named as such in 1963. It is said that Deux-Montagnes gets its geographic name from the two mountains that coureurs des bois, voyageurs and, before them, American Indians, could see from the northwestern shores of the lake after the portage from Sainte-Anne-de-Bellevue. One of them is the Calvaire Mountain and the other, its twin, is Saint-Joseph-du-Lac Hill.