The CN Tower will open its doors to the public on Friday, marking the 50th anniversary of a structure that has become an iconic symbol of Canadian engineering.
Conceived in the early 1970s to demonstrate the strength of national industry, the tower was designed to surpass the height of any existing building at the time, ultimately becoming the world’s tallest freestanding structure upon its completion.
The project’s core team included architect Edward Baldwin, structural engineer Roger Nicolet, structural designer Franz Knoll, site engineer Frank Tam, mechanical engineer Jules Petrinec, electrical engineer Jim Armstrong, and foundation specialists Andre Jordan and Jack Whyte of the Foundation Company of Canada.
Construction relied on a slipform technique, in which concrete was poured into a continuously rising mold to create the tower’s tapered silhouette. Early testing revealed that the concrete did not set quickly enough, causing a loss of material and requiring a restart of the pour.
Work began on 6 February 1973 with a crew of 1,537 workers operating five days a week. The main structure was completed by 22 February 1974, and the antenna was added on 2 April 1975. The project cost $63 million and the tower now weighs approximately 117,910 metric tonnes.
Standing at 1,815.5 feet (553.33 metres), the CN Tower held the title of the tallest tower, building, and freestanding structure from 1976 until 2010, and remains the tallest building in the western hemisphere. It has been recognized by the American Society of Civil Engineers as one of the Seven Wonders of the Modern World.
Team members credit a collaborative atmosphere for the project's smooth execution, noting that the absence of major disputes or litigation was unusual for a venture of this scale.
Key construction figures include 40,524 cubic metres of concrete, 998 kilometres of post‑tension steel, 4,535 metric tonnes of reinforcing steel, and 544.2 metric tonnes of structural steel. The tower contains 1,776 stairs, and its Edge Walk platform, weighing 46,875 kilograms, holds a Guinness World Record for the highest external walk on a building.
Reflecting on the achievement, Franz Knoll expressed pride in completing the tower without significant problems, emphasizing the innovative technology and teamwork that enabled a structure never before attempted.
