At the time of New France, the boulevard LaSalle was called the chemin du Roy and was the first vehicle road in the history of New France. It ran along the north shore of the St. Lawrence River, therefore linking Québec City and Montréal. In 1737, the chemin du Roy covered a distance of 280 km, through 27 seigneuries, including Montréal. The boulevard LaSalle was therefore part of this historic route which today has become a heritage and tourist route.

The boulevard LaSalle was also the main road connecting the Village of Lachine to Montréal and many travellers used it to get to Lachine, from where they departed for the Pays-d’en-Haut (Upper Country)—the Great Lakes area today. It is also this road that the colonists of New France took to go and mill their grain at the flour mill in Lachine. During the French regime, the inhabitants had to maintain this road by means of forced labour.

The chemin du Roy underwent a name change under the English regime to become the Lower Lachine Road. The Lower Lachine Road existed in relation to the Lachine Road (rue Saint-Patrick today) and the Upper Lachine Road (present-day rue Saint-Jacques). During this very long time, this road would be the only land route enabling Verdunites to get to Montréal without any problems. The Lower Lachine Road was named boulevard LaSalle around 1910.