On September 11, 2001, two of four hijacked planes were flown into the Twin Towers of the original World Trade Center, and the towers subsequently collapsed. 7 World Trade Center collapsed due to fires and structural damage caused by heavy debris falling from the collapse of the Twin Towers. The other buildings within the World Trade Center complex were damaged beyond repair and soon after demolished. The collapse of the Twin Towers caused extensive damage to other surrounding buildings and skyscrapers in Lower Manhattan, and resulted in the deaths of 2,606 people, in addition to those on the planes. Since 2001, most of Lower Manhattan has been restored, although there has been controversy surrounding the rebuilding. Many rescue workers and residents of the area developed several life-threatening illnesses that have led to some of their subsequent deaths. A memorial at the site was opened to the public on September 11, 2011, and the museum opened in 2014. In 2014, the new One World Trade Center, at and formerly known as the Freedom Tower, became the tallest building in the Western Hemisphere, while other skyscrapers were under construction at the site.