Architects are always competing to design the world’s tallest building. After designing, constructing, and completing the building, there is usually already a new project in the works to become the next tallest building. And the qualifications are detailed—for example, an antenna cannot add height, but a spire is considered a part of the building.

On this day, December 23rd, in 1970, the North Tower of the World Trade Center is opened. The completion earned the building the title of the tallest building in the world at the time with a height of 1,368 feet.

The North Tower held the title as the tallest building in the world for two years, but the Sears Tower surpassed it in 1973. However, the Tower retained the record for the greatest number of floors. The North Tower’s 110 floors was only surpassed in 2009 when the 163-floor Burj Khalifa was built in Dubai. The World Trade Center towers were a recognizable pair of skyscrapers on the New York City skyline, and the North Tower was distinguishable from its twin by the 360-foot-tall antenna atop its roof.