CN Tower
"Guinness World Records" has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower". Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once, it has also listed it under "tallest tower", omitting it from its list of "tallest buildings." In 1996, Guinness changed the tower's classification to "World's Tallest Building and Freestanding Structure". Emporis and the Council on Tall Buildings and Urban Habitat both listed the CN Tower as the world's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title of world's tallest building to Taipei 101, which is shorter than the CN Tower. The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below).
History of the world's tallest buildings
The skyscraper was invented in Chicago in 1884 when the Home Insurance Building was constructed using a steel-frame with curtain walls instead of load-bearing walls. For the next hundred years, the world's tallest building was always in the United States with New York City accumulating 86 years, and Chicago accumulating 30 years. After just over a century (1885–1998), the distinction moved to the Eastern Hemisphere. Malaysia was the first country to break the United States' record of constructing the tallest buildings in the world when the Petronas Twin Towers were completed in 1998. Taiwan's Taipei 101 was the next building to hold the record, beginning in 2004.