Willis Tower - Height

Height

The Willis Tower remains the tallest building in the Americas and the Western Hemisphere. With a pinnacle height of 1729 feet (527 m), it is the second tallest freestanding structure in the Americas, as it is 86 feet (26 m) shorter than Toronto's CN Tower, and is the only other freestanding structure in the Americas to exceed 1500 feet (457.2 m) in height. As of September 2011, the Willis Tower is the seventh tallest freestanding structure in the world (by pinnacle height), after the Burj Khalifa, the Tokyo Skytree, the Abraj Al Bait Towers, the Canton Tower, the CN Tower and the Ostankino Tower.

At 1,482.6 feet (451.9 m) tall, including decorative spires, the Petronas Twin Towers in Kuala Lumpur, Malaysia, laid claim to replacing the Sears Tower as the tallest building in the world in 1998. Not everyone agreed, and in the ensuing controversy four different categories of "tallest building" were created. Of these, Petronas was the tallest in the first category (height to top of architectural elements, meaning spires but not antennas) giving it the title of world's tallest building.

Taipei 101 in Taiwan claimed the record in three of the four categories in 2004 to become recognized as the tallest building in the world. Taipei 101 surpassed the Petronas Twin Towers in spire height and the Sears Tower in roof height and highest occupied floor. The Sears Tower retained one record: its antenna exceeded the Taipei 101's spire in height. In 2008, the Shanghai World Financial Center claimed the records of tallest building by roof and highest occupied floor.

On August 12, 2007, the Burj Khalifa in Dubai, United Arab Emirates was reported by its developers to have surpassed the Sears Tower in all height categories.

When completed, One World Trade Center in New York City is expected to surpass the Willis Tower through its structural and pinnacle heights, but not by roof, observation deck elevation or highest occupied floor. Burj Khalifa currently holds (by a significant margin) all height records, surpassing the Sears Tower, the CN Tower, One World Trade Center, Taipei 101 and Shanghai World Financial Center in every category. The Chicago Spire, which had a planned height of 610 m (2,000 ft) was expected to lay claim to all categories of height records in the Americas upon completion, but the project was later cancelled in 2010 due to major setbacks.

Until 2000, the Sears Tower did not hold the record for the tallest building by pinnacle height. From 1969 to 1978, this record was held by the John Hancock Center, whose antenna reached a height of 1,500 ft (457.2 m), or 49 ft (14.8 m) taller than the Sears Tower's original height of 1,451 ft (442 m). In 1978, One World Trade Center became taller by pinnacle height due to the addition of a 359 ft (109.3 m) antenna, which brought its total height to 1,727 ft (526.8 m). In 1982, two antennas were installed on top of the Sears Tower which brought its total height to 1,707 ft (520.3 m), making it taller than the John Hancock Center but not One World Trade Center. However, the extension of the Sears Tower's western antenna in June 2000 to 1,730 feet (527 m) allowed it to just barely claim the title of tallest building by pinnacle height.