Lake St. Clair is in Ontario.
Lake St. Clair ( Lac Sainte-Claire ) is a freshwater lake that lies between the Canadian province of Ontario and the U.S. state of Michigan . Ontario . These are the Rainy River , the Pigeon River , Lake Superior , the St. Marys River , Lake Huron , the St. Clair River , Lake St. Clair , the Detroit River , Lake Erie , the Niagara River , Lake Ontario and along the St. Lawrence River from Kingston , Ontario , to the Quebec boundary just east of Cornwall , Ontario .