September 16, 1975 - CN Tower Construction Continues in Toronto

By September 16, 1975, you're witnessing the CN Tower in its final construction phase. Workers had already topped off the concrete shaft at 553 meters earlier that spring, and the Sikorsky S-64 Skycrane "Olga" had lifted the last antenna piece into place on April 2, 1975. Over 1,500 workers kept operations running 24 hours a day to make it the world's tallest freestanding structure. There's much more to uncover about how this landmark came together.

Key Takeaways

• The CN Tower was topped off at 553 meters on April 2, 1975, but interior finishing and completion work continued well into 1975.
• Construction began February 6, 1973, meaning by September 1975 the project had been underway for approximately 31 months.
• The public opening did not occur until June 26, 1976, confirming significant construction activity remained after topping-off.
• Over 1,500 workers operated on rotating 24-hour shifts, five days a week, maintaining continuous progress throughout the project.
• The broader construction timeline spanned 40 months total, placing September 1975 firmly within the active construction period.

How CN Tower Construction Progressed From Groundbreaking to Topping-Off

Construction crews broke ground on the CN Tower on February 6, 1973, kicking off one of the most ambitious engineering projects in Canadian history.

Following this groundbreaking timeline, workers excavated 56,000 tons of earth and shale to a depth of 49.2 feet, confirming the site could support the world's tallest structure.

The foundation techniques involved pouring 7,000 cubic metres of concrete reinforced with 450 tons of rebar and 3 tons of steel cable, reaching 22 feet thick and completing in four months.

Workers then raised a slipform platform 20 feet daily, forming the 335-metre concrete shaft.

By February 1974, the tower became Canada's tallest structure.

A Sikorsky helicopter named Olga was used to lift 39 antenna pieces into place in March 1975, completing the tower's upper structure.

Construction topped off on April 2, 1975, just 26 months after breaking ground. The entire project employed 1,537 workers operating 24 hours a day, five days a week to meet this timeline. Today, resources like concise fact finders make it easy to explore key historical details about landmark projects such as this one, including dates, categories, and country of origin.

How Over 1,500 Workers Kept CN Tower Rising Around the Clock

Keeping the CN Tower rising required over 1,500 workers rotating through 24-hour shifts, five days a week, for 40 months straight.

The shift logistics kept progress continuous, pushing the structure skyward until its April 2, 1975 topping-off. Worker demographics skew older today, with many iron workers now in their seventies and eighties.

Here's what drove this operation:

• Multiple crews rotated around the clock, eliminating downtime
• Iron workers climbed without harnesses, earning pay premiums for high-risk tasks
• Crews managed 10–12 crane lifts per tower section
• The $63 million project launched in 1973 and hit its August 1974 main level milestone

Workers earned a base pay of $8 per hour, with height premium pay adding $1 extra per hour for every 300 feet worked above 1,000 feet. You can see how disciplined scheduling and a large, experienced workforce transformed an ambitious timeline into reality.

The tower's main support pillar was constructed using a hydraulically raised slipform, with concrete poured continuously Monday through Friday to maintain the upward momentum the project demanded. Managing the enormous volume of concrete used throughout construction required precise measurement, much like how engineers today rely on tank volume calculators to accurately determine storage and material capacities in large-scale infrastructure projects.

How the Concrete Shaft and Antenna Came Together

While those 1,500 workers kept the tower climbing skyward, the real story lies in the concrete and steel that made it possible.

You'd start with 7,000 m³ of poured concrete, 450 t of rebar, and 36 t of steel cable anchoring a 6.7 m thick foundation 15 m deep.

From there, slipform jacks pushed the shaft upward continuously, with concrete curing as each layer climbed.

By February 1974, the main shaft had reached Skypod level, topping out February 22.

Workers then raised brackets in August 1974 to support the seven-storey sphere above. The SkyPod working platform relied on 12 brackets and 45 steel rod climbers of type 2510-40-UD-W, specially equipped for strand lifting operations.

The final challenge was antenna hoisting — a Sikorsky S-64 Skycrane lifted 39 separate pieces in March 1975, completing installation on April 2.

That work pushed the tower to 553 m, claiming the world's tallest freestanding structure title. The tower had begun on a CN railway siding, part of the broader Metro Centre redevelopment vision for surplus rail lands in downtown Toronto.

Much like the Continental Congress resolution that formally established the United States Marine Corps in 1775, the CN Tower's construction required deliberate institutional planning and coordinated resources to bring an ambitious project to completion.

How the Antenna Lifted CN Tower Past Every Structure on Earth

By March 1975, the final push to make CN Tower the world's tallest freestanding structure came down to 44 antenna sections and one helicopter.

The Sikorsky Skycrane "Olga" handled all helicopter logistics, lifting each lightweight section individually onto the tower's top with precision. Before the final lift, crews invited public signatures on the last piece.

Here's what you should know about the antenna installation:

• Olga first removed the massive construction crane before starting antenna lifts
• Sections were designed to extend the tower to 533.33 meters
• March 31, 1975 marked the tallest freestanding status milestone at 9:52 a.m.
• April 2, 1975 saw the final section lifted into place

That single month of lifts pushed CN Tower past every structure on Earth. The tower's total construction required 40 months of work with more than 1,500 workers operating 24 hours a day, five days a week.

How CN Tower Went From Construction Site to Global Icon

When the final antenna section locked into place on April 2, 1975, CN Tower's transformation from construction site to global landmark had already begun. You can trace its rise in cultural symbolism directly to its engineering audacity — 553.3 meters of reinforced concrete that made every competing structure obsolete overnight.

Canadian National Railway's $63 million investment wasn't just infrastructure. It became Toronto's most powerful tourism branding asset, drawing international attention long before the public opening on June 26, 1976. Once visitors arrived, the tower's observation and broadcast capabilities gave them a reason to stay engaged.

When Canada's government assumed ownership in 1995, the tower's identity solidified further — no longer a private structure, but a national symbol that continues defining Toronto's skyline for the world.