NEW YORK — It was all so simple for King Kong, the giant ape who fled his captors by clambering to the top of the Empire State Building.

Back then, there was no question that the Manhattan icon was America’s tallest skyscraper.

But that was before Sept. 11, 2001, when the destruction of the World Trade Center towers sparked a rebuilding effort that included vows to produce a new “tallest skyscraper” for the country: a 1,776-foot-high building designed to pack a symbolic punch and serve as a memorial to those killed in the attacks.

That was also before spires, antennas and accouterments made it much harder to determine which building could be called the “tallest.”

Enter the Council on Tall Buildings and Urban Habitat, which today is scheduled to issue its ruling on the latest “tall building” issue. Depending on the outcome, the decision could upend building ratings from China to Chicago.

At issue is whether the 408-foot spire and beacon atop One World Trade Center should be considered part of the building’s height. If so, the skyscraper, scheduled to open in Lower Manhattan in 2014, would measure 1,776 feet. Without the spire, it stands 1,368 feet tall — the same height as the former One World Trade Center structure.

If the spire is included, it would bump Chicago’s Willis Tower — formerly the Sears Tower — from the No. 1 U.S. spot. The Chicago building measures 1,729 feet with its antennas and 1,451 feet without them.

None of this would have mattered had the architects of One World Trade Center, Skidmore, Owings & Merrill, not changed the slender, glassy building’s design in 2012 to remove material that would have enclosed the spire and made it indisputably part of the building. The redesign shaved millions of dollars in construction costs and ensured easier maintenance of the spire.

The Port Authority of New York and New Jersey, which owns the land on which the building sits, and the architects say the multitiered spire is more than a communications antenna because it features a beacon with 288 50-watt LED modules and will emit a light visible for 50 miles on a clear night.

To underscore its argument that the spire is no mere ornament, the Port Authority tested the beacon Friday night, and it heralded the spire’s ceremonial placement atop the skyscraper last May.

The spire also made 1 World Trade Center the third highest skyscraper in the world, according to the Council, after buildings in Dubai, United Arab Emirates, and Mecca, Saudi Arabia.