One World Trade Center technically became New York City's tallest building today.

One World Trade Center, also known as the Freedom Tower, became New York City's tallest building today as workers erected steel columns on the 100th floor to make it 21 feet taller than the Empire State Building's observation deck. When it's completed, the building will be 104 stories tall with a 408-foot spire, for a total height of 1,776 feet.

Watch this cool time-lapse video of the first 1,271 feet of One World Trade Center being built.