The Tower, according to Guiness: 

What better honour is there than to be the first, the best, the highest or the fastest in the world at something? 

It was 9:52 in the morning on March 31st, 1975, that the CN Tower officially became the World's Tallest Free-Standing Structure. This was according to Ross McWhirter, then the editor of the Guinness Book of World Records, who was on site to witness the placement of one of the last sections of antenna. Three days later, the last piece of antenna was attached bringing the overall height to 553.33 metres or 1815 feet, 5 inches. 

Since then, the Tower has added the following distinction: 

■ World's highest 'wine cellar' - 351 metres (1151 ft.)

■  For over three decades the CN Tower is proud to have held the distinction as the World’s Tallest and according to the 2010 Book of Guinness World Records it remains the World’s Tallest Tower*.

■ On November 8, 2011 EdgeWalk at the CN Tower was presented with the Guinness World Record for the “Highest External Walk on a Building”

* World’s Tallest Tower is defined by both GWR and the Council on Tall Buildings and Urban Habitat as “a building in which less than 50% of the construction is usable floor space”.