Thirteen years after the 9/11 terrorist attack, the resurrected World Trade Center has opened for business – marking an emotional milestone for both New Yorkers and the nation.
The 104-story, $US3.9 billion ($A4.2 billion) skyscraper dominates the Manhattan skyline.
Publishing giant Conde Nast became the first commercial tenant in America's tallest building, beginning work at 1 World Trade Center on Monday.
It's the centrepiece of the six-hectare site where the decimated twin towers once stood and where more than 2700 people died on September 11, 2001, buried under smoking mounds of fiery debris.
"The New York City skyline is whole again, as 1 World Trade Center takes its place in Lower Manhattan," said Patrick Foye, executive director of the Port Authority of New York and New Jersey, which owns both the building and the World Trade Center site.
The agency began moving into neighbouring 4 World Trade Center last week.
He said 1 World Trade Center "sets new standards of design, construction, prestige and sustainability; the opening of this iconic building is a major milestone in the transformation of Lower Manhattan into a thriving 24/7 neighbourhood".
With construction fences gone and boxes of office equipment in place, the company moved into what Foye called "the most secure office building in America".
Prior to the move, Conde Nast addressed any issues employees might have had about moving into the tower.
The architectural firm, TJ Gottesdiener of the Skidmore, Owings & Merrill, says it took extra measures to strengthen the steel-and-concrete structure.
It says it is a much stronger structure than the twin towers.
Startingon Monday, more than 170 employees moved into five of Conde Nast's 25 floors, the company said. By early 2015, about 3000 more staffers will move in.
The eight-year construction of the 541-metre high skyscraper came after years of political, financial and legal infighting that threatened to derail the project.
