When did the St. Lawrence Seaway open to shipping?

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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 St. Lawrence Seaway officially opened to shipping in 1959. This project, a joint undertaking by Canada and the United States, created a continuous, deep-draft navigable waterway connecting the Atlantic Ocean to the Great Lakes, effectively opening the industrial and agricultural heartlands of North America to international maritime trade.123