AP

NEW YORK (AP) — Thirteen years after the 9/11 terrorist attack, the resurrected World Trade Center is again opening for business — marking an emotional milestone for both New Yorkers and the United States as a whole.

Publishing giant Conde Nast will start moving Monday into One World Trade Center, a 104-story, $3.9 billion skyscraper that dominates the Manhattan skyline. It is America's tallest building.

It's the centerpiece of the 16-acre site where the decimated twin towers once stood and where more than 2,700 people died on Sept. 11, 2001, buried under smoking mounds of fiery debris.

"The New York City skyline is whole again, as One World Trade Center takes its place in Lower Manhattan," said Patrick Foye, executive director of the Port Authority of New York and New Jersey that owns both the building and the World Trade Center site.

He said One World Trade Center "sets new standards of design, construction, prestige and sustainability; the opening of this iconic building is a major milestone in the transformation of Lower Manhattan into a thriving 24/7 neighborhood."

With construction fences gone and boxes of office equipment in place, Conde Nast CEO Chuck Townsend planned to walk Monday into what Foye calls "the most secure office building in America."

Only about 170 of his company's 3,400 employees are moving in now, filling five floors of the tower, said Patricia Rockenwagner, a Conde Nast vice president and spokeswoman. About 3,000 more will arrive by early 2015.

The building is 60-percent leased, with another 80,000 square feet going to the advertising firm Kids Creative, the stadium operator Legends Hospitality, the BMB Group investment adviser, and Servcorp, a provider of executive offices.

The government's General Services Administration signed up for 275,000 square feet and the China Center, a trade and cultural facility, will cover 191,000 square feet.

From the northeast corner of the site, the tower overlooks the National September 11 Memorial & Museum built in the footprints of the twin towers. Its stated aim is to honor those who perished on that sunny September morning.

For years, the grisly pit where workers found mostly body parts was dubbed Ground Zero of the aerial terror attack.

Now, the illuminated spire of One World Trade Center serves as a beacon to planes that fly over the city, seemingly at eye level with the high rise's open rooftop. The view stretches from Manhattan to the Statue of Liberty into New Jersey and Connecticut and all the way to the Atlantic Ocean.

At night, the incandescent steel-and-glass behemoth can be seen from vessels in New York Harbor approaching Manhattan.

An observation deck eventually will be open to the public.

The eight-year construction of the 1,776-foot-high skyscraper came after years of political, financial and legal infighting that threatened to derail the project.

The bickering slowly died down as two other towers started going up on the southeast end of the site: the now completed 4 World Trade Center whose anchor tenant is the Port Authority, and 3 World Trade Center that's slowly rising.

The spirit of renewal did not quash memories of the horrific act of terror, but the area has prospered in recent years beyond anyone's imagination. About 60,000 more residents now live there — three times more than before 9/11 — keeping streets, restaurants and shops alive even after Wall Street and other offices close for the day.

Still, it's a bittersweet victory, one achieved with the past in mind as the architects created One World Trade Center.

T.J. Gottesdiener of the Skidmore, Owings & Merrill firm that produced the final design told the Associated Press that the high-rise was built with steel-reinforced concrete that makes it as terror attack-proof as possible.

He said the firm went beyond the city's existing building codes to achieve that.

"We did it, we finally did it," he said.