One World Trade Center is officially the tallest building in New York City.
Construction crews erected steel columns to form a girder that will eventually become the 100th floor of the building on Monday.
The structure now stands a little more than 1,250 feet tall, topping the Empire State Building.
Upon completion one world trade will stand a symbolic 1,776 feet, becoming the tallest building in the United States and the second tallest in the world behind the Burj Khalifa Building in Dubai.
