It was lifted onto the 104-story building on Wednesday.
Nine of 18 giant steel pieces of the spire arrived at the site in New York City Tuesday via barge from Port Newark, N.J.
The arrival marked the end of a 1,500-nautical-mile journey that started in Canada on Nov. 16.
A plant outside Montreal produced the 18 pieces. The spire will make the tower the tallest building in the Western Hemisphere.
The remaining nine pieces of the 408-foot, $20 million spire are being trucked in from Canada and another plant in South Plainfield, N.J.
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