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How did construction of the St. Lawrence Seaway change riverside communities?

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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.

The construction of the St. Lawrence Seaway was a massive civil engineering project that significantly altered the landscape and daily lives of those living in riverside communities. To facilitate the creation of the deep-draft waterway and associated hydroelectric power infrastructure, approximately 6,500 people were forced to relocate from their homes.1

Beyond the displacement of residents, the physical environment of these communities underwent extensive modification. The project required the raising of bridges and the construction of new tunnels, dikes, and roads to accommodate the altered river geography. The creation of the 48-km (30-mile) long Lake St. Lawrence, which resulted from the construction of the Moses-Saunders Power Dam and the Iroquois Control Dam, further transformed the local terrain. These efforts were essential to overcoming navigational hazards and tapping the river's energy, ultimately integrating these regions into a major international shipping route.12