The still-under-construction One World Trade Center has gone past 1,250 feet, surpassing the Empire State Building as New York’s tallest skyscraper. Once the tower is completed, its spire will rise 1,776 feet into the air, and the structure probably will be declared the tallest building in the United States—and the third highest in the world. But it still has a long way to go to join these skyscrapers.