The CN Tower is a concrete communications tower in downtown Toronto, 553.33 meters (1,815 feet) tall, built by Canadian National Railway. Work began on February 6, 1973, the structure was finished on April 2, 1975, and the tower opened to the public on June 26, 1976. It was the world’s tallest free-standing structure for more than three decades, although sources differ on the year it lost that title.
Why Canadian National built a tower
According to the official CN Tower history, Toronto went through a construction boom in the 1960s. The city’s existing transmission towers were too short to send radio and television signals over the new buildings. Canadian National, the railway company, decided to build a taller tower to solve the problem and, in the company’s own words, to showcase Canadian innovation and industry.
The railway had a practical reason to take on the project. It owned the Railway Lands, a large area of former rail yards between Front Street and Lake Ontario, and the tower was planned for that ground. The land itself had been reclaimed from the lake over the previous century, so the foundation work had to deal with fill, shale, and the proximity of the shoreline.
Construction, 1973 to 1975
Crews moved onto the site on February 6, 1973. The CN Tower history says they removed more than 56 metric tonnes of earth and shale to prepare the foundation. Canadian National employed more than 1,500 workers over 40 months to complete the structure.
The main shaft is a hexagonal concrete core. Concrete was poured into a slipform, a moving mold that rose on hydraulic climbing jacks, so the shaft grew continuously instead of being built in separate lifts. The concrete portion reaches 335 meters (1,100 feet). By February 1974 the tower was already the tallest structure in Canada. In August 1974 work began on the seven-story sphere that holds the observation decks and the 360 Restaurant.
The antenna came last. In March 1975 a heavy-lift helicopter named Olga lifted 39 pieces of the antenna into place. The tower was finished on April 2, 1975, which is also the date the official history gives for its certification by Guinness World Records as the world’s tallest free-standing structure.
Opening on June 26, 1976
The tower was complete in 1975, but the public did not enter until the following year. The CN Tower history gives June 26, 1976, as the opening date to the public. At least one other account describes a separate official ceremony later in 1976, so the phrase “opening day” can refer to either event depending on the source.
Height records and how they changed
The CN Tower history states that at 553 meters (1,815 feet) it was the tallest free-standing structure in the world until Burj Khalifa in Dubai surpassed it in 2009. Another widely used reference, Wikipedia, gives a different date. It says the title passed on September 12, 2007, when Burj Khalifa, still under construction, grew taller than the Toronto tower. The two dates measure different things: one counts the completed building, the other the moment the height was passed during construction.
The tower also held the title of world’s tallest tower. According to the same Wikipedia entry, Canton Tower in Guangzhou (604 meters) took that distinction in 2009, and Tokyo Skytree (634 meters) is listed with an even greater height since 2011. A tower is a structure built mainly to carry antennas or to be observed from, a category separate from habitable skyscrapers, which is why Burj Khalifa and the towers appear in different record lists.
Ownership and later additions
Canadian National owned the tower until 1995, when it was sold to Canada Lands Company, a federal Crown corporation, according to the CN Tower history. Later additions changed how visitors use it. The glass floor was installed in 1994 at 342 meters (1,122 feet), and the EdgeWalk, an outdoor walk around the pod, opened on August 1, 2011. Both dates come from Wikipedia and were not confirmed on the official history page, which gives no dates for either feature. In 1995 the American Society of Civil Engineers named the tower one of the Seven Wonders of the Modern World, as reported by the same reference.
Today the tower still does the job it was built for. The official history says it carries signals for more than 17 Canadian television and FM radio stations, employs more than 500 people year-round, and welcomes more than two million visitors a year.
Timeline
| Date | Event |
|---|---|
| February 6, 1973 | Construction begins on the Railway Lands |
| February 1974 | Tallest structure in Canada |
| August 1974 | Work starts on the seven-story sphere |
| March 1975 | Antenna lifted into place by helicopter |
| April 2, 1975 | Tower finished |
| June 26, 1976 | Opens to the public |
| 1994 | Glass floor installed (Wikipedia) |
| 1995 | Ownership passes to Canada Lands Company |
| 2007 or 2009 | Burj Khalifa passes its height, depending on the source |
| August 1, 2011 | EdgeWalk opens (Wikipedia) |
Frequently asked questions
When was the CN Tower built?
Construction started on February 6, 1973, and the structure was finished on April 2, 1975. It opened to visitors on June 26, 1976.
Why was the CN Tower built?
Canadian National built it to carry radio and television signals above the tall buildings that were rising in 1960s Toronto, and to show Canadian engineering and industry.
How tall is the CN Tower?
The official history gives 553 meters (1,815 feet). Wikipedia’s record table lists 553.33 meters.
Is the CN Tower still the tallest in the world?
No. It lost the title of tallest free-standing structure to Burj Khalifa, in 2007 or 2009 depending on the source, and the title of tallest tower to later towers listed above.
Last verified: October 2026
Sources
- CN Tower, “Building a Canadian icon” (official history)
- The Canadian Encyclopedia, entry “CN Tower” (consulted for construction start and height)
- Wikipedia, entry “CN Tower” (glass floor, EdgeWalk, alternative record dates)
Related reading
- Toronto history hub: the city from York to today
- Timeline of how the city grew
- Other historic buildings of Toronto
- Where the nickname “the Six” comes from
- The story behind the airport code YYZ
Cite this page
APA: History of Toronto. (2026, October 23). CN Tower History: Why and When Toronto’s Tower Was Built. http://localhost:8210/blog/the-fascinating-history-of-toronto-cn-tower-from-its-construction-to-become-one-of-the-worlds-most-iconic-landmarks
MLA: “CN Tower History: Why and When Toronto’s Tower Was Built.” History of Toronto, 23 Oct. 2026, http://localhost:8210/blog/the-fascinating-history-of-toronto-cn-tower-from-its-construction-to-become-one-of-the-worlds-most-iconic-landmarks. Accessed .
Chicago: History of Toronto. “CN Tower History: Why and When Toronto’s Tower Was Built.” Last modified October 23, 2026. http://localhost:8210/blog/the-fascinating-history-of-toronto-cn-tower-from-its-construction-to-become-one-of-the-worlds-most-iconic-landmarks.
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