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Construction and Operation of Locks


Locks are engineered systems, often part of a connecting channel, used to overcome changes in water level. Locks operate by taking in a downbound ship at an upstream water level, closing the gates on the lock, letting water out to lower the ship to the downstream water level and then opening its gates to allow the ship to proceed. The reverse process occurs for upbound boats. Currently, 3 lock systems, containing a total of 20 locks, are operated on the Great Lakes / St. Lawrence Seaway system.

Click the image below to see an animation of a lock. Use your "Back" button to return to this page.

Lock Animation

Go to EXPLOREEXPLORE: Take a Virtual Tour of a Lock to see how it works! Follow the link "Interactive Tour - Gateway to North America."