The Canso Causeway (Cabhsair Chanso in Gaelic) Coordinates: 45°38′38″N61°25′11″W / 45.64389°N 61.41972°W is a 1,385 m (4,544 ft) rock-fill causeway crossing the Strait of Canso, connecting Cape Breton Island by road to the Nova Scotia peninsula. Its crest thickness is 40 m (130 ft), carrying the two vehicle traffic lanes of the Trans-Canada Highway, Nova Scotia Highway 104 on the mainland side, and Nova Scotia Highway 105 on the Cape Breton side, as well as the single track mainline of the Cape Breton and Central Nova Scotia Railway.
Constructed in an "S" shape, the causeway has a base width of 244 m (801 ft) in waters having a maximum depth of 65 m (213 ft).
Cape Breton Island remains circumnavigable as a result of the 24 m (79 ft) wide and 570 m (1,870 ft) long Canso Canal, which is located at the eastern end of the causeway to allow ship traffic to transit the Strait of Canso. The 94 m (308 ft) Canso Canal Bridge is a swing bridge which carries the road and railway line across the canal.
The word "Canso" is believed to be derived from the Mi'kmaq word kamsok, which means "opposite the lofty cliffs."
On July 2, 2014, it was announced that the Government of Canada would transfer ownership of the causeway to the Nova Scotia provincial government. The federal government will still maintain the Canso Canal and the navigational locks. 
Prior to the construction of the causeway, Cape Breton Island was connected to the mainland by separate railway car and motor vehicle ferries.
In 1880, the Intercolonial Railway (ICR) was opened between Mulgrave on the Nova Scotia side, west to New Glasgow. In 1890, the ICR built a line from Point Tupper on the Cape Breton side, east to Sydney. As a result, a rail ferry service was necessary so that rail cars from Cape Breton Island could be interchanged with the mainland North America rail network. Initially a small 2-railcar barge was used, however the growth of traffic from Industrial Cape Breton soon mandated that a dedicated rail ferry service be established. This service was operated by the ICR until 1918 when the ICR was merged into Canadian National Railways (CNR). CNR operated the ferries from 1918 until the causeway opened in 1955. Vessels used included: Mulgrave (1893–1901), Scotia (1903–1955), and Scotia II (1915–1955). 
Various private passenger and horse-drawn carriage ferry services operated between Point Tupper or Port Hawkesbury or Port Hastings to the Nova Scotia side. By the 1930s, the Nova Scotia Department of Transportation took responsibility for providing the automobile ferry service. By the 1940s, as a result of war-time travel growth, as well as the growing popularity of automobiles, the service was expanded to 24 hours/day. Toward the end of the service in the 1950s, vessels included the George H. Murray, John Cabot, Ponte de Canseau, and Sir Charles Tupper.
In the late 1890s and early 1900s, the Industrial Cape Breton region was experiencing unprecedented economic growth as a result of multiple coal mines and two large integrated steel mills having opened. The Scotia rail car ferry that entered service in 1901 was struggling to keep up with the demands despite operating 24-hours per day year-round. In 1903, an ambitious proposal was presented to the provincial and federal governments, a proposal known as the "Strait of Canso Bridge", detailing a plan to build a 4,370 ft (1,330 m) steel cantilever bridge at the narrowest portion of the strait to carry the Intercolonial Railway's main line between Sydney and Truro.  The span, measuring 1,800 ft (550 m), would have been longer than the Firth of Forth Bridge and roughly similar in size to the Quebec Bridge. 
From 1947 to 1951, articles and cartoons in provincial newspapers indicated that the strait's crossing was to be a bridge. Finally, project engineers agreed that because of the size, the amount of ice, the strength of the currents that filled the Strait of Canso every winter, and the depth of the water, it would be difficult to construct a bridge, and instead, a causeway option was chosen. 
The Canso Causeway was built at a narrow location on the Strait of Canso, about 6.6 kilometres (4.1 mi) northwest of Port Hawkesbury and Mulgrave,  crossing from Cape Porcupine near Auld's Cove on the Nova Scotia side to Port Hastings on the Cape Breton side. About 10,092,000 t (9,933,000 long tons) of rock for building the causeway was quarried from a mountain on Cape Porcupine.
Contracts were awarded from May 1952 to build approach roads and rail lines for the causeway construction, and the project was officially started at a ceremony on September 16, 1952 that was attended by federal Minister of Transport Lionel Chevrier and Premier of Nova Scotia Angus L. MacDonald. 
The Strait of Canso was permanently blocked on December 10, 1954, and construction continued through the winter on building the roadway and railway line, as well as finishing the Canso Canal and its swing bridge.  Construction was finally completed on April 13, 1955, when the railway line and the roadway were finished at a cost of $22 million.
The first train across the causeway was a Canadian National Railways work train, led by steam locomotive #2639 on April 18, 1955. The railway line across the causeway entered active service on Saturday, May 14, 1955, when the first revenue train was a 10-car passenger train, led by steam locomotive #6014, and the rail ferry service from Mulgrave to Point Tupper was then discontinued. The roadway across the causeway opened to vehicle traffic on May 20, 1955, when the vehicle ferry service was discontinued.
The official opening of the Canso Causeway took place on August 13, 1955  when several thousand people attended ceremonies which included a gala parade of what was meant to be 100 bagpipers heralding Cape Breton's road connection to the North American mainland, however, the 100th bagpiper refused to pipe. 
When the causeway was completed, the eastern end of the Strait of Canso became ice free during the winter. Several industries were attracted to the Point Tupper area, including the Stora pulp and paper mill, a Gulf Oil refinery and a heavy water plant.
Aside from blocking sea ice, the blocking of the Strait of Canso caused significant environmental damage from the enormous changes in the tidal regime of the southern Gulf of St. Lawrence all the way to the mouth of the St. Lawrence River.[ citation needed ] The causeway also had the effect of damming the waterway for migrating ground fish stocks for decades until some of these species were able to determine how to get around Cape Breton Island into the gulf. In addition, the causeway allowed several non-native species of land animals access onto Cape Breton Island. One particularly troublesome interloper has been the bobcat, which has slowly forced the more gentle lynx out of its traditional hunting grounds and up into the Cape Breton Highlands. 
From 1955 to the early 1990s, the Canso Causeway charged a toll to motorists. The toll was discontinued after the construction costs (approximately $23 million) were paid off.
In 1993, CN Rail sold its Truro-Sydney railway line which crossed the Canso Causeway to the Cape Breton and Central Nova Scotia Railway. Today, CB&CNS employees operate the swing bridge across the Canso Canal.
The Strait of Canso is a strait located in the province of Nova Scotia, Canada. It divides the Nova Scotia peninsula from Cape Breton Island.
The Intercolonial Railway of Canada, also referred to as the Intercolonial Railway (ICR), was a historic Canadian railway that operated from 1872 to 1918, when it became part of Canadian National Railways. As the railway was also completely owned and controlled by the Government of Canada, the Intercolonial was also one of Canada's first Crown corporations.
Havre Boucher is a community in Antigonish County, Nova Scotia, Canada.
The Cape Breton and Central Nova Scotia Railway is a short line railway that operated in the Canadian province of Nova Scotia. CBNS operated of main line and associated spurs between Truro in the central part of the province to Point Tupper on Cape Breton Island.
The Canso Canal is a short canal located in Nova Scotia, Canada.
Grand Narrows is a community in the Cape Breton Regional Municipality in Nova Scotia, Canada. The community is the birthplace of the longest serving Premier of Nova Scotia, George Henry Murray. The Barra Strait Marina is here, operated by the Grand Narrows Waterfront Development Society.
Mulgrave is a town on the Strait of Canso in Guysborough County, Nova Scotia, Canada. Located along the Marine Drive, Route 344 traverses the community. The town's current name was adopted in 1859 to honour the colonial Lieutenant Governor, the Earl of Mulgrave. Lying opposite to the town of Port Hawkesbury, the community is located along the western shore of the Canso Strait. It was established as McNair's Cove in the early 19th century, and the name Port Mulgrave was adopted in 1859, later shortening to its current form. The early industry of the community relied on ferry service between the Nova Scotia mainland and Cape Breton Island. Ferry service began in the 1810s and rail service reached the area in the 1880s. The ferry services lasted until the opening of the Canso Causeway in 1955, dealing a major blow to the local economy. As of 2016, Mulgrave has a population of 722 and a population density of 40.5/km2 (104.9/sq mi), within an area of 17.83 km2 (6.88 sq mi).
Point Tupper is a rural community in Richmond County, Nova Scotia, on the Strait of Canso, in western Cape Breton Island.
Enterprise Cape Breton Corporation (ECBC) was a Canadian federal Crown corporation which promoted and coordinated economic development throughout Cape Breton Island and adjacent areas in the eastern Nova Scotia town of Mulgrave.
Port Hastings is a unincorporated settlement on Cape Breton Island, within the Municipality of the County of Inverness, Canada. The population in 2021 was 90.
The Canso Canal Bridge is a rotating swing bridge in Nova Scotia, Canada. It crosses the Canso Canal at the eastern end of the Canso Causeway, connecting the Nova Scotia peninsula to Cape Breton Island. The bridge carries the 2 traffic lanes of Highway 104 as well as a single track railway line operated by the Cape Breton and Central Nova Scotia Railway (CBNS).
Melford International Terminal is a proposed Canadian marine-rail container terminal to be built in the community of Middle Melford in Guysborough County, Nova Scotia.
Henry Nicholas Paint was a Canadian politician, shipowner and merchant.
The Point Tupper Generating Station is a 150 MW Canadian electrical generating station located in the community of Point Tupper in Richmond County, Nova Scotia.
The Barra Strait is a 1.22 km (0.76 mi) wide channel located in the Canadian province of Nova Scotia. It connects the northern and southern basins of Bras d'Or Lake, an inland saltwater body that dominates the centre of Cape Breton Island. The border between two of Cape Breton Island's counties runs through the strait; the community of Grand Narrows, in Cape Breton County, is situated on the eastern shore while the community of Iona, in Victoria County is situated on the western shore.
The Grand Narrows Bridge is a Canadian railway bridge crossing between Victoria County, Nova Scotia, and Cape Breton County. At 516.33 m (1,694 ft), it is the longest railroad bridge in the province. The bridge incorporates a swing span at its eastern end to permit the continued passage of marine traffic through the strait.
Lennox Passage is a navigable waterway between Cape Breton Island and Isle Madame in Nova Scotia, Canada. Small craft use the relatively protected Passage traveling to and from St. Peters Canal at the village of St. Peter's and the Strait of Canso to avoid sailing around the east coast of Cape Breton in the open Atlantic Ocean.
Balache Point Lighthouse also known as Balache Point Range Rear Lighthouse is an active Canadian lighthouse located next to the Canso Canal, near Port Hastings, Inverness County, Nova Scotia. The salt shaker style light, which sits on a small hillock on the Cape Breton side of the canal, is the second lighthouse to be built on the site.
The Barra Strait Bridge is a Canadian road bridge crossing the Barra Strait of Bras d'Or Lake, carrying Nova Scotia Route 223 between Iona, Victoria County, on the West side, and Grand Narrows, Cape Breton County on the east side. The bridge incorporates a double leaf bascule section at its eastern end to permit the continued passage of marine traffic through the strait.
The Municipality of the County of Inverness is a county municipality on Cape Breton Island, Nova Scotia, Canada. It provides local government to about 17,000 residents of the historical county of the same name, except for the incorporated town of Port Hawkesbury and the Whycocomagh 2 Miꞌkmaq reserve, both of which are enclaves. Public services are provided in the areas of recreation, tourism, administration, finance, and public works.