September 11 attacks
The damaged part of the Pentagon was rebuilt within one year of the attacks. Construction of One World Trade Center started on April 27, 2006. It reached its full height on May 20, 2013. The spire was installed on top of the building at that date. This makes the total height of 1 WTC's at 1,776 feet (541m). This makes it the tallest building in the Western Hemisphere. One WTC finished construction and opened on November 3, 2014.