It was the party planned for a century. 

Gov. Andrew M. Cuomo and MTA Chairman Tom Prendergast hosted elected officials, including Mayor Bill de Blasio and others for a New Year's Eve subway soiree at the new 72nd Street station on Second Avenue. 

Guests, including labor representatives and transit advocates, packed onto the station's mezzanine to toast the completion of the avenue's three new stations at 72nd, 86th and 96th streets, slated to officially open to the public before noon on Jan. 1 — nearly 96 years after the idea to run a train under the avenue was first pitched. 

They then filled a 96th Street-bound Q train for the inaugural subway ride under Second Avenue, stopping at 86th and 96th street stations for brief tours. 

"We need to show people that government works and we can still do big things," said Cuomo, who had publicly pressured the Metropolitan Transportation Authority to complete the project by his revised deadline of Jan. 1. "This is New York and there is nothing we can't do when we put our mind to it. That's what we have to remember."

Hors d'oeuvres like salmon napoleon and radish wraps with smoked tofu made the rounds before the ball dropped as revelers sipped local libations produced in New York State. Several bars on the station's mezzanine carried wines and spirits. A newsstand's racks were lined with bottled beers from the likes of Brooklyn Brewery and Saranac. 

"This isn't your grandfather's subway," Prendergast said. "I can honestly tell you that ... there were two things that I never expected would happen. One was the Cubs winning the World Series. The second was having a gala New Year's Eve celebration for the opening of the Second Avenue line."

The bright station lights were swapped for moodier blues, purples and pinks that illuminated the arched ceiling of 72nd Street. Queens blues group Sunnyside Social Club belted tunes as guests filtered in. But behind the ritz of the evening was a good amount of grit, said U.S. Transportation Secretary Anthony Foxx. 

"Very few places around the country are thinking as boldly as New York is," Foxx said. "Whether it's Gateway, LaGuardia, Tappan Zee, this — this is what our department should be doing. And we can't do it without our local partners who are thinking big and willing to grit it out.”

"That's what this project represents — a lot of grit," he added. 

Conductor Charlie Feliciano and motorman Joey Morales operated the inaugural Q train, which was wrapped with colorful subway bullet decals that read "The Second Avenue Subway." The wrapped trains will continue to be used once service launches on Sunday, Cuomo's office said. 

For $4.5 billion, the MTA built about two miles of track and three new stations. It's only a fraction of the entire line that has been dreamed up, but experts expect a huge change once service starts. 

"It's so important because this shows that when you invest in public transit, you get results," said John Raskin, executive director of the transit advocacy group Riders Alliance. “I think the new subway line will make a marked difference in people's lives — not just in the Upper East Side, it’s for anyone who rides the Lexington Avenue line."