After the park-facing façade of the Plaza Hotel had glowed with the number “100,” after white and gold jets of light had been launched from the roof into the dark October sky, and after a pigeon and a heart-shaped balloon had flown past the 12th floor, suddenly flashes of white light, syncopated to the strains of “One” from the Broadway hit “A Chorus Line,” burst from the windows of the venerable hostelry-turned-hotel-and-condominium.

The Plaza’s 100th birthday last night was a hit, and it gave a new meaning to the term “Great White (and Green) Way.” The sidewalks of Fifth Avenue and Central Park South were jammed for an outdoor celebration that lit up the building with 600,000 lumens of light in hues of white, silver, and gold.

“This is a big holiday for New York, for everyone,” the owner of the building, the founder and chairman of Elad Properties, Isaac Tshuva, said early in the evening, standing next to a fully manned check-in desk and a huge vase of yellow and pink dahlias set on a marble-topped table in the lobby (even though the hotel isn’t open yet). Surrounded by his family, he beamed all night long, especially during his Champagne toast: “L’Chaim to you and to the city of New York,” he said to his guests during a private reception in the Edwardian Room.

About an hour later, at the podium outside the hotel, Mr. Tshuva joined Deputy Mayor Daniel Doctoroff for the countdown to the fireworks show. Mr. Doctoroff, acting mayor during Mayor Bloomberg’s trip to Europe, noted the mayor had just arrived back in New York before reading a city proclamation declaring October 1 as the Plaza’s 100th birthday.

Screens throughout Grand Army Plaza projected photographs from the Plaza’s past, and remarks included sentimental moments. And the square itself was lit up to show off a grove of Bradford Callery pear trees whose care Mr. Tshuva’s company endowed through a contribution to the Central Park Conservancy.

The president of the New York Hotel Trades Council, Peter Ward, recalled having his wedding at the hotel 24 years ago.

Mr. Ward also spoke of his initial “concern and skepticism” about the intentions of Elad Properties with regard to the future of the union employees of the hotel.

“But then I sat down with Mr. Tshuva and we achieved an agreement that represents fairness and equity,” Mr. Ward said. The occasion made an impression on many. “I’ve seen so many ground-breakings and topping offs, and I’ve never seen anything like this,” a construction business veteran, John Tishman, said.

“This is good for New York. Through the complex process of the renovation, we became partners with the owners,” the commissioner of city’s Department of Buildings, Patricia Lancaster, said.

“The only other party like this I remember attending is the Brooklyn Bridge’s one-hundredth,” the commissioner of the city’s Landmarks Preservation Commission, Robert Tierney, said.

An illustrator, Hilary Knight, brought along a copy of the first book about the Plaza’s most famous resident, “Eloise: A Book for Precocious Grown-ups,” written by Kay Thompson and drawn by Mr. Knight.

“Eloise is over 50 years old, so half the age of this building. She looks great, and so does the building,” Mr. Knight said. “It makes me happy this building will never change. That’s reassuring in a city being ripped apart.”

“This is a tribute to New York and it is a measure of the man and his family,” a vice chairman of Lehman Brothers, Harvey Krueger, said of Mr. Tshuva.

The ceremony before the fireworks included Israeli singer Shalva Berti singing the theme from “Love Story” (with the Israeli flag flying to her right, acknowledging the Tshuva family’s home country), and actor Matthew Broderick, who introduced Mr. Tshuva (the pronunciation of whose name Mr. Broderick was observed practicing earlier in the evening).

“Like ‘a-choo-vah,’ without the a,” the chief executive of Elad Properties, Miki Naftali, instructed the “Producers” star.