NEW YORK (AP) — One World Trade Center, the monolith being built to replace the twin towers destroyed in the Sept. 11 attacks, claimed the title of New York City's tallest skyscraper on Monday, as workers erected steel columns that made its unfinished skeleton a little over 1,250 feet high, just enough to peek over the roof of the observation deck on the Empire State Building.City officials and iron workers applauded as the first 12-ton column was hoisted onto the tower's top deck."This project is much more than steel and concrete. It is a symbol of success for the nation," said David Samson, chairman of the Port Authority, the agency that owns the World Trade Center.Clear skies afforded an immaculate 360-degree view from the top, although it wasn't easy getting up there. After riding an elevator to the 90th floor, a small group of officials and journalists had to climb three steep ladders to reach the top platform, which was encircled by blue netting along the perimeter.The milestone is a preliminary one. Workers are still adding floors to the building once called the Freedom Tower. It isn't expected to reach its full height for at least another year, at which point it is likely to be declared the tallest building in the U.S., and third tallest in the world.