One World Trade Centre, at 451 metres, is indeed taller than the Willis Tower in Chicago, which measures 442 metres. That judgment was delivered by the official arbiter of structural stature, the Council on Tall Buildings and Urban Habitat.
The main issue was whether a 408-foot needle atop the One World Trade Center would be counted in the total height of the tower.
Project chief architect David Childs and the rest of the One World Trade Center team convinced the council's height committee that the spire was, itself, architectural. The designers noted that the top of the new building's steel parapet is located at 1,368 feet, the height of the original World Trade Center Tower 1. The spire reaches from that parapet to the new building's height of 1,776 feet.
One World Trade Center's height to its architectural top is 1,776 feet (541.3 meters), according to the ruling. Chicago’s Willis Tower's architectural height is 1,451 feet (442.1 meters).