<Dd> b . Skidmore, Owings & Merrill . </Dd> <P> One World Trade Center (also known as 1 World Trade Center, 1 WTC or Freedom Tower) is the main building of the rebuilt World Trade Center complex in Lower Manhattan, New York City . It is the tallest building in the Western Hemisphere, and the sixth - tallest in the world . The supertall structure has the same name as the North Tower of the original World Trade Center, which was destroyed in the terrorist attacks of September 11, 2001 . The new skyscraper stands on the northwest corner of the 16 - acre (6.5 ha) World Trade Center site, on the site of the original 6 World Trade Center . The building is bounded by West Street to the west, Vesey Street to the north, Fulton Street to the south, and Washington Street to the east . </P> <P> The building's architect was David Childs, whose firm Skidmore, Owings & Merrill (SOM) also designed the Burj Khalifa and the Willis Tower . The construction of below - ground utility relocations, footings, and foundations for the new building began on April 27, 2006 . One World Trade Center became the tallest structure in New York City on April 30, 2012, when it surpassed the height of the Empire State Building . The tower's steel structure was topped out on August 30, 2012 . On May 10, 2013, the final component of the skyscraper's spire was installed, making the building, including its spire, reach a total height of 1,776 feet (541 m). Its height in feet is a deliberate reference to the year when the United States Declaration of Independence was signed . The building opened on November 3, 2014; the One World Observatory opened on May 29, 2015 . </P> <P> On March 26, 2009, the Port Authority of New York and New Jersey (PANYNJ) confirmed that the building would be officially known by its legal name of "One World Trade Center", rather than its colloquial name of "Freedom Tower". The building is 104 standard floors high, but the tower has only 94 actual stories . </P>

When did they start building the new world trade center