Split from the rest of the province by the St. Lawrence River, Quebec's southern arm extends itself over Vermont, Maine and New Brunswick before finally ending in the river's gulf, which has the distinction of being the largest estuary in the world. The fertile river valley is the province's most populated area, and as the St. Lawrence acted as one of the main entry points for exploration of the interior of North America, the area's communities and landscapes factor heavily in Canada's history. (continue...)