Most lists of big buildings are based on height. By that measure, the Burj Khalifa in Dubai is highest at 2,717 feet tall. The tallest American building on the list, which ranks sixth in the world, is One World Trade Center, which is 1,776 feet tall.
Another means of measurement is how much floor area a building covers, based on square feet. By that yardstick, the largest building by far is the Pentagon, America’s military headquarters, built in 1943. It is followed by the FCA US LLC Headquarters and Technology Center, operated by Fiat Chrysler, which covers 420,000 square feet. It is based in Auburn Hills, just outside Detroit. Third, the Willis Tower skyscraper in Chicago covers an area of 416,000 square feet spread over a building that is 1,451 feet tall with 108 stories.
The official purpose of the Pentagon is that it is the headquarters of the U.S. Department of Defense. The department is the largest agency in the United States, with 703,000 civilian employees. According to the Architect’s Journal, the Pentagon got its name because it is built with five sides, and it stands seven stories tall. It has 131 stairways and 19 escalators. Britannica says about the Pentagon’s design: “There are 17.5 miles (28 km) of corridors, but, because of its innovative construction, it is possible to walk between any two points within the building in approximately seven minutes.”
The Pentagon is well known for a reason beyond its size. On September 11, 2001, when two commercial aircraft were flown into the World Trade Centers, another, a Boeing 757, crashed into the western side of the Pentagon at 9:37 EDT. The crash killed those who hijacked the plane and 184 people between the plane and the building.