Located between Lake St. François and Lake St. Louis, the “Coteau rapids” are the narrowest and most turbulent of all the rapids along the route, a spot where voyageurs had to portage their canoes. Around 1750, a “rigolet” canal was built to facilitate the transport of furs from trading posts.

Later, while the American Revolution was raging, rebel forces invaded Canada. The British had difficulty resupplying their troops who were protecting the border near the Great Lakes. A canal had to be built.

In 1781, the Coteau-du-Lac canal went into operation, making it possible to bypass the two-metre vertical drop of the rapids. From the moment it opened, the canal served both military and commercial purposes.

After it was replaced by the Beauharnois canal in 1845, the fortified Coteau-du-Lac canal was finally abandoned by the military in 1856. The site then served several different purposes until it was declared a site of national historic significance in 1923 and opened to the public in 1967.