About Lock 21

Lock 21 lies under 60 feet (18.3 m) of water in the St. Lawrence, near Long Sault, Ontario. The tops of the piers are at 40 feet (12 m). The current is strong: in the lock I measured about 35 feet per minute (10.7 m/min) in June 2024; it is stronger over the spillway.

Depth60 ft (18.3 m)

Tops of the piers40 ft (12 m)

Chamber270 × 45 ft

Rebuilt1883–1886

FloodedJuly 1, 1958

Lock 21 was the last lock of the Cornwall Canal, at its upstream head, at the village of Dickinson’s Landing. The canal, opened in the early 1840s, bypassed the Long Sault rapids from Cornwall to Dickinson’s Landing, over about 11 miles.

It was a guard lock: no difference in level between upstream and downstream. The one we dive today dates from the canal’s enlargement, rebuilt from 1883 to 1886: a chamber 270 feet by 45 (82 m by 14 m), and a spillway at its upstream end.

Lock 21 around 1904: the canal, its bank on the left and the lock’s works in the distance — Lock 21 around 1904. Source: Seaway History

On July 1, 1958, the Robert H. Saunders dam, built for the St. Lawrence Seaway, flooded the lock, Dickinson’s Landing and other villages along the shore: the Lost Villages. Their people had been moved to Long Sault and Ingleside.

In 1988 and 1989, Nick Baets and the Ottawa chapter of Save Ontario Shipwrecks dived the lock and drew it. His 1988 drawing is the basis of the site zones.

Lock 21 drawn by Nick Baets: the lock, the weir and its sluice gates, the divers’ entry from Macdonell Island, the ropes and the current — Nick Baets' plan of Lock 21, displayed at the divers' pavilion on Macdonell Island (after Save Ontario Shipwrecks' field guide, 1989). Source: David Gibbins, *Diving Lock 21*

To learn more

Dickinson’s Landing, Lost Villages Historical Society: the village’s history, its stagecoaches, boats and canal
Lost Villages of the St. Lawrence, Ontario Heritage Trust
Cornwall Canal and Dickinson’s Landing, Wikipedia
Save Ontario Shipwrecks, Ottawa chapter