History of the world's tallest buildings
The buildings that were the tallest secular skyscrapers, which excludes religious buildings, were:
The list of tallest buildings is based on the default metric of the Council on Tall Buildings and Urban Habitat (CTBUH), that of measuring to the highest architectural element. Other criteria would generate a different list. Shanghai World Financial Center is not on the above list, but it surpassed Taipei 101 in 2008 to become the building with the highest occupied floor. Using the criteria of highest tip (including antennae), the World Trade Center in New York City was the world's tallest building from 1972 to 2000, until the Sears Tower in Chicago (which already had a higher occupied floor than the World Trade Center) had its antenna extended to give that building the world's tallest tip; a title it held until the 2010 completion of Burj Khalifa. Petronas Towers and Taipei 101 were never the world's tallest buildings by the highest–tip criteria.
CN Tower
The CN Tower is the tallest freestanding structure in the Western Hemisphere. As of 2013, there are only two other freestanding structures in the Western Hemisphere which exceed in height; the Willis Tower in Chicago, which stands at when measured to its pinnacle; and the topped-out One World Trade Center in New York City, which has a pinnacle height of , or approximately shorter than the CN Tower. Due to the symbolism of the number 1776 (the year of the signing of the United States Declaration of Independence), the height of One World Trade Center is unlikely to be increased. The proposed Chicago Spire was expected to exceed the height of the CN Tower, but its construction was halted early due to financial difficulties amid the Great Recession, and was eventually cancelled in 2010.