The first lock canal in North America

Captain William Twiss, commanding Royal Engineer of the British army, initiated and supervised construction of the Coteau-du-Lac canal to speed the passage of batteaux past the most treacherous rapids on the St. Lawrence above Montréal. For thousands of years Amerindians had portaged around these rapids, and in the mid-18th century the French had built a dike or rigolet there, but the canal became the third solution to the navigation problems at Coteau-du-Lac. Built in 1779-1780, it measured more than 100 m long and had three locks, each 1.8 m wide with a navigable depth of about 80 cm, overcoming an approximately 2 m difference in water level between the upper and lower ends of the rapids, and it was the first lock canal in North America. Though used to full capacity as soon as it opened, it did not solve all navigation problems on the St. Lawrence above Montréal, and in 1783 the Faucille, Trou-du-Moulin, and Rocher-Fendu canals were built in the same sector. These first canalization works on the river greatly eased navigation by allowing vessels to bypass the most troublesome section of the waterway, where the 12.8-km stretch between lakes Saint-François and Saint-Louis had a total drop of 25.6 m, the greatest difference in level anywhere on the St. Lawrence River. Twiss had begun his British army career at age 15, completed his training as a military engineer during his first posting to the Fortress of Bilgraltar, was sent to Canada in 1776, and carried out many engineering projects including this canal, three other military canals on the St. Lawrence, and fortifications at Québec, Sorel, Saint-Jean, and Ile-aux-Noix. After returning to England in 1783, he won the admiration of his superiors by completing a series of forts intended to protect the country from the threat of invasion by the armies of Napoleon.

Quebec · Canada