The Construction of the St. Lawrence Seaway
Impressive for its immense scale, organizational complexity, and speedy completion, the construction of the St. Lawrence Seaway from 1954 to 1959 was an outstanding engineering achievement. This project, which included hydroelectric power generation and water-level control, transformed shipping on the St. Lawrence River above Montréal by allowing ocean going vessels access to the Great Lakes. Acting in close cooperation, the Canadian and American governments coordinated the planning and construction needed to complete this remarkable undertaking on the world's longest inland waterway.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.