History

Building a Canadian icon

Acknowledging the land and water that the CN Tower stands on

Two men wave their hats at a sign saying “CN Tower” to mark the beginning of the Tower’s construction in February 1973. — Tower construction begins in 1973

The CN tower story

The 1960s ushered in an unprecedented construction boom in Toronto, a city quickly growing up from a regional hub to a thriving, cosmopolitan destination. Existing transmission towers were simply not high enough to broadcast radio and television signals over the tall new buildings, which bounced the signals away from their intended audience.

To solve this problem—and to demonstrate the aspirations of Canadian innovation and industry—Canadian National, the Crown corporation that operated the country’s largest railway network, employed more than 1,500 workers for 40 months to build the CN Tower. Once completed, it would be the tallest tower in the world, capable of broadcasting signals far and wide across the region.

Construction begins

Planners identified the Railway Lands between Front Street and Lake Ontario as the ideal site of construction. CN Railway owned this parcel of land, which had been reclaimed from Lake Ontario over the previous century, and used it as their primary railyard in downtown Toronto for decades, watching the city grow up around it.

Tower construction crews moved in on February 6, 1973, and started to remove over 56 metric tonnes of earth and shale for the foundation. Once the foundation was ready, work began on the CN Tower’s 335-metre (1,100-foot) concrete shaft, a hexagonal core with three curved support arms.

To produce the CN Tower’s tapered contour, construction crews poured concrete into a massive mold known as a slipform. As the concrete hardened, the slipform, supported by a ring of climbing jacks powered by hydraulic pressure, moved upwards, gradually decreasing in size to impart the curve in Tower.

A crane helps to build the base of the CN Tower, covered in scaffolding, in July 1973. — The slipform rising, 1973

A south-facing aerial view of the CN Tower shows that it is now a few hundred feet tall in October 1973. — Aerial view of the Tower, 1973

By February 1974, the Tower was already the tallest structure in Canada. In August 1974, work began on the seven-storey sphere that would eventually house the observation decks and the revolving 360 Restaurant.

As construction of the Tower continues, the tapered shape of the shaft starts to take form in August 1974. — Raising the main pod framing, 1974

Topping it off

The CN Tower approached completion in March 1975, when Olga, the giant Sikorsky helicopter, flew into the city to lift the 39 pieces of the antenna into place. The CN Tower was finished on April 2, 1975, opening to the public on June 26, 1976. At 553 metres (1,815 feet), it would remain the tallest freestanding structure in the world until surpassed by Dubai’s Burj Khalifa in 2009.

A Sikorsky helicopter named Olga lowers the antenna onto the top of the CN Tower in March 1975.

A photo taken from the outside of the Tower shows the helicopter, named Olga, hovering above the Tower in March 1975.

In 1995, Canadian National sold the CN Tower to the Canada Lands Company, a federal Crown corporation specializing in attractions of national interest. It was then that the tower truly became Canada’s National Tower—both in name and deed.

Today, the CN Tower is the centre of telecommunications for Toronto, serving more than 17 Canadian television and FM radio stations; we’re also the workplace of more than 500 people throughout the year, and—of course—an internationally renowned tourism destination, welcoming more than two million visitors each year.