At the ceremony Monday, workers unfurled an American flag as a crane lifted the final steel beam 977 feet in the air and set it in place. Onlookers cheered along with about 1,000 construction workers.
"It felt good, a lot of satisfaction, a lot of pride rebuilding what was destroyed," construction worker Larry Miller told the Wall Street Journal.
Four World Trade Center is slated to be the first skyscraper to be completed in the 16-acre World Trade Center site, which will open in the fall of next year.
Developer Larry Silverstein thanked the workers, or as he called them, "the people who built this place with their own hands."
"You work every day, rain or shine, to reclaim the skyline, to give New Yorkers back the city that the terrorists tried to take away," he said.
The New York Times reported the building, to be the sixth-tallest skyscraper in New York upon its completion, was designed to be understated.
"This is a special place with sacred meaning, and we felt we had to be respectful," project architect Osamu Sassa said.
Tokyo firm Maki and Associates are behind the monolithic design, orchestrated to nearly vanish from the skyline from certain angles when the light is right.
"We like the idea of the building dematerializing," Sassa said.
The twin towers of the World Trade center were destroyed Sept. 11, 2001, when al-Qaida terrorists hijacked four passenger jets and rammed two of them into the iconic skyscrapers. A third hit the Pentagon and the fourth was forced to crash in a Pennsylvania field after passengers attacked the hijackers.