It's in traveller's tales, from the XVIIIth century that we find the name St.Lawrence. However, the American Indians called it «The river that walks», long before.

The first Europeans to venture on the St-Lawrence named it «The cod River» or «Large River». But it is to Jacques Cartier, who sailed it in his second voyage to America, that western historians attribute the river's official discovery. Departing from Saint-Malo in 1535, the navigator arrived in the gulf after a two month trip. To commemorate the Tricentenary old landing, a cross was raised in the Cartier-Brebeuf Parc in Old-Limoilou, in Quebec City. Finally, it is Samuel de Champlain, Quebec City's founding father, that imposed the name of St.Lawrence to identify the waterway that constitutes the St.Lawrence River, even though the name could already be found in traveller's tales dating back to the XVIIth century, and in many writings and maps from the mid-XVIth century.

Nevertheless, this large river has been called many names, like: France Prime, Canada River, Mayne River [...] before finally being named St.Lawrence.

Some history
The St.Lawrence played a fundamental role in Canada's and Quebec's history. From the XVIIth century, the establishment of the fur trade marked a turning point in North-America's history. Contrary to fishing which is praticed from the shore line, the fur trade involved deep penetration inside the territory and its sedentary occupation. The American Indians saw their lifestyle change drastically. The French, drawn by the prospect of gains, advanced deeper and deeper into the Laurentian Valley in search of new trading grounds.

During the XVIIth century, the St.Lawrence is the major player and host to many expeditions. In 1603 Samuel de Champlain takes part in the first expedition to go up the St.Lawrence; he then thinks of establishing the future colony in Trois-Rivières (south of Quebec City). Finally, it is during a new mission, for the purpose of establishing a residential base along the river, that Champlain chose the detroit of Kebec(Quebec) where he built his first house in july 1608.
 

Currently, many efforts are being made by the Federal Governement(Canada) to reduce the pollution within its waters and thus save from extinction some threatened species such as the so very precious Beluga (or white whale; sea mammel living in arctic waters).