Construction began in 1963 and it opened on March 11, 1967. Named for the respected Lower Canada political reformer Louis-Hippolyte Lafontaine, the Lafontaine Tunnel is an immersed tube structure, measuring 1,391 m (4,563.6 ft) long. It carries the Autoroute 25 expressway and passes beneath Île Charron (Îles de Boucherville & entrance/exit #1 of Autoroute 25), as well as the main shipping channel in the St. Lawrence River immediately downstream from the St. Lawrence Seaway.
Each section weighs 32,000 tons, is 110 metres (360 ft) long, 37 metres (121 ft) wide and rises to a height of 8 metres (26 ft). In total, the bridge–tunnel is 1.8 kilometres (1.1 mi) long. It is estimated that 44 million vehicles drive through it per year, or 120,000 per day. The tunnel was built with prefabricated sections and placed in dry dock in the river, 24 metres (79 ft) below the surface of the water. It is one of the largest prestressed concrete structures in the world.
In 1960, the construction of the Trans-Canada Highway (TCH) through Quebec from the Ontario border to Rivière-du-Loup was announced. In Montreal, to avoid having to build a huge bridge that would have disfigured the city and destroyed a neighborhood, the engineers opted for the construction of a tunnel located under the bed of the St. Lawrence River, and dug a trench for the file under the bed river and buried 4.6 metres (15 ft) to 6.1 metres (20 ft) from the ground. The construction was completed in March 1967, just before the opening of Expo 67. Construction cost $75 million.
It bears the name of Louis-Hippolyte La Fontaine, a politician born in 1807 in Boucherville.
