The 3.8 billion dollar building took eight years to build and is currently the tallest building in the United States, reported the BBC.
The 104-storey-tall building is 60 percent leased and the government's General Services Administration has signed up for 275,000 square feet.
Patrick Foye, executive director of the Port Authority, remarked in a statement that the New York City skyline is "whole again." He added that it is "the most secure office building in America."
The 1,776ft (541m) tall skyscraper which is stationed at the centre of the 16-acre site where the twin towers once stood, includes a memorial in the footprints of the old towers and a museum, opened this year.
An observation deck at the top of the building will eventually be open to the public.
TJ Gottesdiener of the Skidmore, Owings and Merrill firm that developed the final design said that the skyscraper has gone beyond the city's existing building code, and has been built with steel-reinforced concrete.
More than 2,700 people were killed in the attack.