Lake St. Francis is a large lake located on the St. Lawrence River in Ontario, Canada, and New York, USA. It is part of the St. Lawrence Seaway and serves as a significant waterway for shipping and recreation. The lake is known for its scenic beauty and diverse wildlife, making it a popular destination for fishing, boating, and birdwatching. The lake covers an area of approximately 30 square miles and has a maximum depth of about 30 feet. It is surrounded by several towns and communities, providing access to various amenities and recreational activities. The lake plays an important role in the local economy and ecosystem.