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How did canals and locks bypass the Cedar Rapids, Cascades Rapids, and Lachine Rapids?

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Map showing the St. Lawrence hydrographic system and the five main sectors of the St. Lawrence Seaway project, stretching from Lake Ontario near Kingston through various locks, canals, and dams along the Canada-United States border to Montreal. The map highlights key locations such as the Thousand Islands, International Rapids, Lake St. Francis, Soulanges, and Lachine sections, with detailed labeling of major locks, canals, and power dams. Cross sections of the lock and canal system are depicted — St. Lawrence Seaway The St. Lawrence hydrographic system, with the five main sectors of the St. Lawrence Seaway project.

To bypass the Cedar, Cascades, and Lachine rapids, the Canadian government constructed two canals and five locks as part of the St. Lawrence Seaway project.

These engineering works were essential to overcoming the navigational hazards posed by the river's swift-flowing sections and were part of a broader effort to create a waterway with a navigation depth of 8.2 metres (27 feet) between Montreal and Lake Erie. This modern infrastructure replaced an earlier, shallower system that had consisted of six canals and 22 locks limited to a depth of 4 metres (14 feet).1