http://www.bbc.co.uk/news/world-us-canada-17898138 One World Trade Center has become New York's tallest building, overtaking the Empire State Building, after a steel column was lifted into place.
The installation of the column on the 100th floor of the skyscraper makes the structure at the site of the 9/11 attacks 1,271ft (387m) high.
The building, construction of which began in April 2006, will be 1,776ft tall when completed.
The World Trade Center's twin towers were destroyed on 11 September 2001.
The skyscraper, dubbed Freedom Tower, became the tallest building in New York a day before the one-year anniversary of the operation that killed Osama Bin Laden.
'A real milestone'
The rooftop parapet of the building, often referred to as Freedom Tower, will be 1,368ft - exactly the same height as the original One World Trade Center.
But when all 104 floors of the new skyscraper are finished, including the antenna, One World Trade Center will be slightly taller than its predecessor.
On top of the roof, a 408-ft (124-m) cable-stayed spire will be added, making the total height of the structure a symbolic 1,776ft (541m).
With the spire, it will also surpass the Willis Tower (formerly known as the Sears Tower) in Chicago as the tallest building in the US.
Inside, the building will have 69 floors of office space, including restaurants and television broadcasting facilities, as well as an observation deck at the top.
In the shadow of the new tower is the 9/11 memorial, made up of two reflecting pools in the footprints of where the twin towers used to stand.
Mayor Michael Bloomberg celebrated the milestone.
"The New York City skyline is, once again, stretching to new heights," Mr Bloomberg said in a statement.
"Today our city has a new tallest building and a new sense of how bright our future is," Mr Bloomberg said.
The World Trade Center project suffered several delays over designs and naming.
The original One World Trade Center surpassed the Empire State Building's height of 1,250ft in 1970.
Although the new one is set to claim the title of the tallest building in the US, Dubai's Bhurj Khalifa by some stretch is the tallest building in the world.
