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 buildings in New York City
New York has played a prominent role in the development of the skyscraper; since 1890, eleven structures in the city having held the title of world's tallest building. New York City went through a very early high-rise construction boom that lasted from the early 1910s through the early 1930s, during which 16 of the city's 82 tallest buildings were built—including the Woolworth Building, the Bank of Manhattan Trust Building, the Chrysler Building and the Empire State Building, each of which was the tallest in the world at the time of its completion, the last remaining so for forty years.