Once the pouring of the concrete was completed on February 22, 1974, the final stages of building the world's tallest Tower were about to begin.
The last thing to be added to the Tower was the 102 metre (335 foot) steel broadcasting antenna, consisting of 44 pieces - the heaviest weighing 7.26 metric tonnes (8 tons).
Before the antenna could be lifted, however, the giant crane used for four years of round-the-clock service to build the Tower would have to be dismantled and brought down.
To do all this moving, "Olga" - a 10 ton Sikorsky helicopter used primarily for industrial lifting - was flown to Toronto.
And on her first trip, tragedy almost struck.
As Olga was removing the first piece of the boom, the crane lurched, twisting and seizing the supporting bolts.
Now hovering about 1500 feet up, Olga was basically attached to the Tower, with 50 minutes of fuel (the job was supposed to take only 12 minutes). The crane couldn't just be released, either. The operator was still inside.
Steel workers scrambled up and burned off the bolts, finally releasing the crane from the Tower.
Olga landed with about 14 minutes of fuel left.
After this brush with danger Olga performed the rest of the work flawlessly.
As each piece of antenna was raised, workers would stand at the top and help manoeuvre the new piece and bolt into place. And all this where the Tower is only 5 feet in diameter and with gusting winds and freezing temperatures.
It took more than 3 1/2 weeks before the final piece of antenna was secured by high rigger Paul Mitchell on April 2, 1975.
He even danced a little jig to celebrate. 1815 feet above the earth.
Today, the antenna broadcasts over 30 Toronto television and FM radio signals across Southern Ontario in addition to wireless paging and cellular telephone signals.
Plus, the antenna makes us the tallest tower in the western hemisphere.