Fort Lac la Pluie was a fur trade depot established by the North West Company sometime between 1775 and 1787.
It was located on a high bank on the west side of modern Fort Frances, Ontario across from International Falls, Minnesota on the Rainy River downstream (west) of some rapids (Chaudière portage) where the river flows out of Rainy Lake.
They would meet at Grand Portage on Lake Superior, exchange goods and head back before the freezup.
To further save time goods and furs would be shuttled between Grand Portage and Lac la Pluie.
Around 1795 John McKay (fur trader) of the Hudson's Bay Company had a rival post nearby.