The Canso Causeway, opened in 1955….linking mainland Nova Scotia with Cape Breton Island:
In the early 1950’s the face of Cape Porcupine was quarried and the rock-fill placed into the Strait of Canso to provide a roadbed for a highway (now Trans Canada 104) and railway Prior to that there had been car and railway ferries.
It’s 1.4km across with a base width of 244m at the deepest point of 66m. On the Cape Breton side there is a swing-bridge over a ship canal