Several communities call the area surrounding Lake St. Lawrence home. The largest is Cornwall, Ontario’s easternmost city of about 46,900 people. Cornwall's industrial base has shifted to a diverse mix of manufacturing, automotive, high tech, education, food processing, distribution centers and call centers. Other population hubs include South Stormont, a township in eastern Ontario, Canada, in the United Counties of Stormont, Dundas and Glengarry. Communities such as Long Sault, Ingleside, Morrisburg and Iroquois, Ontario, as well as Massena, Wilson Hill, Louisville, and Waddington, New York all border Lake St. Lawrence. The townships of South Dundas and South Stormont stretch along the Canadian shore and St. Lawrence County lies along the US shore. Several islands dotting the lake have significant populations, with many featuring active community associations.
Inundation of the river caused a dozen Ontario communities, now collectively known as the Lost Villages, to be flooded. There was also inundation on the New York side, but no communities were as widely impacted. The Lost Villages are a prominent attraction for visitors and locals. These communities were inundated following unprecedented land expropriation for construction of the St. Lawrence Seaway and Power Project in the 1950s. Their inundation is a point of pride and historical culture for many local residents – especially those affected personally. Many communities were completely rebuilt on higher ground, with several present-day communities such as Long Sault, Morrisburg and Iroquois, Ontario containing houses and other structures moved from areas that were flooded. Upper Canada Village, a park that opened in 1961 depicting life in a rural English-Canadian setting during the year 1866, is a part of the Project’s heritage preservation plan and contains many such structures.
The Mohawk Nation of Akwesasne straddles the intersection of an international border (United States/Canada) and provincial borders (Ontario and Quebec) on both sides of the river, primarily downstream of Lake St. Lawrence. Residents remain closely tied to Lake St. Lawrence and other reaches of the St. Lawrence River nearby.
There are several native – some endangered – as well as invasive species present in Lake St Lawrence. Organizations such as the St. Lawrence River Institute of Environmental Sciences (SLRIES) and the Canadian Wildlife Federation help conserve the local ecology of the area. The lake is home to several species of concern, including threatened and endangered species such as Blanding's turtle, bald eagles, osprey, black tern, and the Indiana bat.
Numerous north-woods mammal species find their home on the shores and islands of the lake, including muskrat, beaver, flying squirrels, mink, deer, porcupine, etc. Winter ice cover on the lake provides important passage for animals between the mainland and islands.
Known as one of the great freshwater sport-fishing grounds in northeastern North America, anglers travel from around the continent to fish for species such as pike, bass (particularly smallmouth bass), and muskellunge.
There are several invasive species in the lake too. Zebra and quagga mussels, round gobies and sea lamprey are the most prominent.
The St. Lawrence River Valley is a key part of the Atlantic Migratory Fly-Way - a main pathway for seasonal migration of many bird species. The region has also been listed as an Important Bird Area by Audubon, New York. Bald eagles, which had not been seen on the lake for many years, are making a comeback and can be seen frequently – especially in the winter.
One principal endangered species is the American Eel, which has experienced a dramatic decline. Lake St. Lawrence provides an important link in their migratory path. SLRIES community outreach helps raise awareness of their plight, and allows citizen scientists to help document sightings and facilitate habitat association.