World Trade Center Towers, 1970s (Creative Commons)

The steel frame of the building remains unfinished, but reaches higher than 1,250 feet, the height of the Empire State Building's highest observation desk. 

CBS News says: The tower still isn't as high as the antenna that sits on the Empire State Building, but when complete will stand at 1,368 feet, beating out the midtown skyscraper that was for decades the world's tallest. When counting a 408-foot-tall antenna spire that will sit on its roof, the "Freedom Tower" will measures 1,776 feet.

Discounting the antenna, it will still be the second-highest building in the U.S., after the Willis Tower in Chicago. (Experts usually don't count antennas or flagpoles when measuring building height.)

CNN has a time lapse video of the building's construction here. 

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