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).
Manhattan
The former Twin Towers of the World Trade Center were located in Lower Manhattan. At , the 110-story buildings were the world's tallest from 1972 until they were surpassed by the construction of the Willis Tower in 1974 (formerly known as the Sears Tower, located in Chicago). One World Trade Center, a replacement for the Twin Towers of the World Trade Center, is currently the tallest building in the Western Hemisphere.