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Road to the Isle: The Canso Causeway

For the week of Monday August 13, 2007

On August 13, 1955, the Canso Causeway officially opened, linking Cape Breton Island to the Nova Scotia mainland.

Canso Causeway Opening, August 13 1955
© CHIN 2007. Gut of Canso Museum & Archives

From the early 16th century, island inhabitants – the Mi‘kmaq peoples, Portuguese and Spanish fishermen, and French, British and Canadian settlers – had depended on boats to cross the Canso Strait with its strong tidal currents and treacherous ice conditions.

In 1901, the Canadian National Railways (CNR) extended its transcontinental rail system to handle Cape Breton Island’s burgeoning production of coal, iron and steel, which had surpassed all other island commerce.  By 1952, this center of Maritime industry produced 38% of Canada’s coal and 18% of its steel. For more than fifty years the CNR used increasingly larger ferries to haul laden railway cars across the strait, but the need for a permanent land-link was continually debated.

Engineer's sketch of a proposed bridge for the Strait of Canso, 1903
© CHIN 2007. Gut of Canso Museum & Archives

Engineers believed the ice floes – up to 175 metres wide, 1.5 kilometres long and travelling at 4 to 7 knots and a current volume greater than the St. Lawrence River – would destroy any bridge link. Finally, in 1952, the Canadian government approved an engineering proposal to build a causeway to link Cape Breton and the mainland. The causeway was S-shaped, 1.6 kilometres long, 25 metres wide at the top, 6 metres above sea level, and contained 9.2 million tonnes of rock fill. It had a depth of 73 metres, and a width of 260 metres at its deepest point, with only 5% visible above sea level. The causeway finished under budget, three weeks early, despite daunting engineering hurdles.   When completed it was the deepest rock-fill causeway in the world.

Canso Causeway - Canal seen from Cape Breton
© CHIN 2007. Gut of Canso Museum & Archives
The Canso Causeway had an immediate and lasting effect on Cape Breton Island’s economic development. When the worldwide coal and steel industry went into decline in the 1960s, the causeway facilitated industrial diversification and a rapid development of tourism, which had already risen from 30,000 to 120,000 people per year. The causeway eliminated the tidal currents allowing the construction of a new island deepwater superport, which quickly attracted pulp and paper, gypsum, refined oil, heavy water, and quarrying enterprises to Cape Breton.

Overcoming the engineering challenges posed by the natural environment of the Strait of Canso made the Building of the Canso Causeway one of the Canada’s greatest engineering achievements. This, coupled with its cultural importance to Cape Bretoners as a symbol of “Homecoming” and “Leaving, but longing to stay” led to its designation as a National Historic Event in 2005.

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