Sault Ste. Marie Ship Canal
Completed in 1895, this canal formed the last link in an all-Canadian navigation system stretching from the St. Lawrence River to Lake Superior. Designed and built by Canadians, the canal incorporated several engineering innovations. It was the world's longest lock and the first to operate with electrical power. It was also novel in using an emergency swing bridge dam to protect the lock in case of accident. Electricity was generated on site in the powerhouse. Closed in 1987 owing to a lock wall failure, the canal was equipped with a modern lock and opened for recreational use in 1998.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.