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).
List of tallest structures in the United States
A common misperception is that landmarks such as the Stratosphere Tower are the tallest United States structures, but they are in fact the tallest "buildings". Likewise Taipei 101 was often misrepresented as the world's tallest structure (although it was the tallest occupied building, before the certification of Dubai's Burj Khalifa as such), but in fact is far eclipsed by antenna towers in over a dozen states in the United States and in other countries.