I’ve always though the St. Lawrence starts at Kingston, Ontario, and that Wolfe and Simcoe Islands are in the river, not the lake.
During an episode of Powerboat Television they mentioned that the "geographic" start of the St. Lawrence River is at the 1000 Islands Bridge near Rockport and Ivey Lea, Ontario (opposite Alexandria Bay, NY). The Kingston newspaper also described this area as the end of Lake Ontario and the start of the river. What is it about this area that makes this the "geographic" start of the river. There is a noticeable drop in elevation in the area of the bridge that causes quite a bit of current.
Max – good answer, and that’s certainly what all my paper and GPS charts indicate. And when you approach Kingston from the main body of Lake Ontario the red buoys are to port, which indicates that you’re heading downstream in a river. If they were marking the entrance to Kingston harbor I would expect them to be to starboard. Anyway, I’ll keep this question active for a while to see if someone has a definitive answer as to the "geography" part of the question.

All of the online encyclopedias (including Wikipedia) say the Saint Lawrence River originates at the outflow of Lake Ontario between Kingston, Ontario on the north bank, Wolfe Island in mid-stream, and Cape Vincent, New York.

As far as the"geographic start" is concerned, water flow, water level, geology and other factors might have been considered. However, the consensus is the St. Lawrence begins at the site mentioned above.

powered by Yahoo Answers