Why it was built — and why it was never used

The War of 1812 exposed a critical weakness in British North America: the St. Lawrence River, the main supply line from the Atlantic to the interior, ran dangerously close to the US border. American raiders had demonstrated they could sever this artery at will. The British response was to commission an alternative route — an inland canal running north from Kingston through the interior of Upper Canada to the new town of Bytown (now Ottawa), then down the Ottawa River to the St. Lawrence above Montreal.

Lt. Col. John By of the Royal Engineers arrived in 1826 to begin the project. It was the largest construction undertaking in British North American history. Working with approximately 2,000 labourers per year — Irish and French-Canadian men — By’s teams carved locks out of solid granite, built masonry dams across rivers, and dug channels through wilderness. The human cost was severe: the low-lying sections near Kingston were malarial, and hundreds of workers died from swamp fever during construction.

The canal opened in 1832. By then, the strategic situation had changed completely. The Rush-Bagot Agreement (1817) had demilitarised the Great Lakes, and the prospect of renewed US-British conflict in North America had faded rapidly. The canal was never used militarily. John By returned to England, was called before a Parliamentary inquiry over cost overruns, and died in 1836 having never received the official recognition his achievement deserved.

Instead of military convoys, the canal carried timber rafts and grain barges. The town of Bytown grew up around the construction camps and the canal head; it was renamed Ottawa in 1855 and became the national capital in 1857. The Rideau Canal’s eight Ottawa locks — still hand-operated today — cascade up the hill directly below the Parliament Buildings, an extraordinary piece of living infrastructure at the heart of Canada’s capital.