The Willis Tower, formerly known as the Sears Tower, is the tallest building in Chicago with a height of 1,451 ft (442 m). The tower was also the tallest building in the world when construction was complete in 1973 (before the Petronas Towers were built in 1998). Designed by Fazlur Khan and Bruce Graham, the skyscraper has 108 floors and took three years to build. It is the second tallest building in America after the One World Trade Center in New York City and the 14th tallest building in the world. Over one million people flock to see the views from its observation deck, known as the Skydeck, every year making it one of the most popular tourist attractions in Chicago.