Hundreds of red, white and blue LED modules illuminated lower Manhattan as officials tested the lights atop 1 World Trade Center.
The Port Authority of New York and New Jersey said Friday the beacon is packed with nearly 300 modules and their glow can be seen for up to 50 miles.
The beacon and spire together stand 408 feet tall and bring the building, formerly called the Freedom Tower, to its symbolic height of 1,776 feet.
The Durst Organization operates the spire, which will serve broadcasters.
A committee of world building heights experts met Friday in Chicago to decide whether a design change that affects the 408-foot needle disqualifies it from being counted as the nation's tallest skyscraper.
Architects for the firm that designed One World Trade Center made their case for the building's spire to be counted towards its height, giving it the full, symbolic measurement of 1,776 feet, and making it officially the tallest in the U.S.
The Council on Tall Buildings and Urban Habitat, a Chicago-based organization considered an authority on such records, is set to decide its official height, and whether the spire can be included.
Without the spire, the building would be considered shorter than the Willis Tower in Chicago, which stands at 1,451 feet and is the tallest in the U.S.
"What we're interested in is that symbolic height ... what's important is the number, 1,776," architect David Childs, who will be making the case before the group, told NBC 4 New York.
The group meets Friday and is expected to decide next week.