During the terrorist attacks of September 11, 2001, hijacked airliners struck the Twin Towers of the World Trade Center in Lower Manhattan, causing severe structural damage and fires that led to progressive collapse. Nearly 3,000 people were killed at the site. The South Tower fell first, followed by the North Tower, and damage and fire also brought down 7 World Trade Center later that day while harming many nearby buildings. Built in 1973 as the world’s tallest buildings, the towers used a framed-tube design. A 2005 federal investigation found the impacts and ensuing fires, not substandard design, caused the disaster and its lasting health and rebuilding consequences.