The CN Tower's construction relied on a Sikorsky helicopter, nicknamed 'Olga,' to lift and place the final sections of its antenna mast, a painstaking process completed by early August 1975. At 553 meters, the freestanding concrete tower became the tallest structure on Earth, a title it held until Dubai's Burj Khalifa surpassed it in 2007. Built as a communications tower, it became Toronto's defining skyline landmark and a major tourist attraction.
The CN Tower began as a practical solution to a mundane problem: Toronto's growing skyscrapers were interfering with television and radio signals across the city. Canadian National Railway proposed a tower tall enough to broadcast cleanly over any future construction, and engineers designed a hexagonal-core concrete structure using a continuous pour technique, slip-forming the concrete in a single unbroken 24-hour-a-day operation for months.
The final, most dramatic phase involved lifting 44 separate antenna sections into place using a Sikorsky S-64 Skycrane helicopter, since building a crane strong enough at that height would have been prohibitively difficult. Pilots hovered with astonishing precision to bolt sections together thousands of feet above the ground.
The tower's observation deck, glass floor, and revolving restaurant later made it a global tourist icon, but its original purpose as a communications relay is largely forgotten by the millions who visit annually. It remains the tallest freestanding structure in the Western Hemisphere.