When “Fiddler on the Roof” first opened on Broadway 50 years ago, “we all thought it was going to close after the Jews had seen it,’’ said Joanna Merlin, who originated the role of Tevye the milkman’s oldest daughter, Tzeitel. “We thought it was a show for Jews.”

Instead, of course, the original production ran almost nine years on Broadway, longer than any musical ever had, and won nine Tonys. First, though, it opened out of town, in Detroit, where it went through a rough month of sanding and smoothing. Then, on Aug. 26, 1964, at the National Theatre, “we opened in Washington and were suddenly a hit,’’ said Austin Pendleton, the first Motel the tailor, who added that “Fiddler” is the only show he’s ever been in that has stayed with him to the point that even now, he has dreams that he’s performing in it.

Backstage at the Town Hall on New York’s West 43rd Street last week, several generations of Anatevkans — performers from that first production, or the movie, or one of the show’s four Broadway revivals — were getting ready to celebrate the musical’s milestone on stage, at a benefit performance for the long-struggling National Yiddish Theatre — Folksbiene.

Chaim Topol, who was playing Tevye on London’s West End in the late ’60s when Norman Jewison cast him in the 1971 movie, was showing he can still “biddy biddy bum.” And at 91, Fyvush Finkel, who played Lazar Wolf in the 1981 revival, was still dancing.

The women who’ve played Tev­ye’s daughters over the decades were out in force: Merlin was practicing a song with Michèle Marsh, who played Hodel in the movie. Rosalind Harris — who played Tzeitel in the movie and on Broadway, where she replaced Bette Midler — was going over some phrasing with former stage sister Adrienne Barbeau — who played Hodel — while Barbeau was getting her hair done.

Several groups of women who’d played sisters had plans to catch up over dinner the next night, and Lori Ada Jaroslow and Donalyn Petrucci Shreve hoped to see Liz Larsen, their sib from the 1981 revival, in her current role in “Beautiful.”

“Can you believe we’re still here?” Mimi Turque-Marre, who played Hodel and later Tzeitel in the original production, said as she embraced Merlin at an earlier reception. Her old friend answered a question with a question: “Do you think maybe it’s because of ‘Fiddler,’ and God smiled on us?”

A universal touchstone

Based on the stories of Sholem Aleichem, with a title inspired by Marc Chagall’s painting “The Fiddler,” the story follows a poor dairyman’s attempts to hold on to what matters as his daughters are rebelling and his whole way of life is disappearing. In 1976, New York Times theater critic Clive Barnes described the show’s book by Joseph Stein and music by Jerry Bock with lyrics by Sheldon Harnick as “absolutely perfect. There is not a song — and in this it is like the only other ‘perfect’ musical, ‘My Fair Lady’ — that you could consider being changed.”

That’s how a show set on a shtetl in czarist Russia became “a touchstone for Jewish Americans and anyone with a connection to themes of change and disruption and family,” said Alisa Solomon, author of the 2013 book “Wonder of Wonders: A Cultural History of Fiddler on the Roof.” “Which is to say, every sentient being.”

The show certainly changed the lives of those it touched first: Pia Zadora, who played Bielke, the youngest of Tevye’s five daughters in the original production when she was just 10, said it taught her what family could be. “I learned to trust, to care and to love” from putting on that show, said the actress, who came to the benefit with her third husband, a Las Vegas police detective she met when filing a complaint against her second husband. “He’s my same age! I didn’t even know that was legal,’’ she joked. And, in the parlance of “Fiddler,” “a perfect match.” (Another of Tevye’s daughters who got one of those is young-looking Neva Small, Chava in the movie, whose matchmaker brought her a dermatologist.)

The life lesson Liz Larsen has never forgotten came as she was learning the dance Chava does when Tevye decides that his Chavaleh is dead to him because she has married a Christian: “I was petrified’’ until the director and choreographer Jerome Robbins advised her to “just move like you are moving through honey, not air.” Done! “It freed me up, and after that I didn’t have to worry about how I looked,” she said. And has that trick worked in other situations? “Always,’’ Larsen said.

Barbeau, who was working as a go-go dancer when she auditioned to play Hodel, said she felt from the moment she went in that she would get the part — a certainty she saw as “a message from my deceased grandmother.” (And no, she said, that’s not a kidding reference to Tevye’s made-up dream, in which Grandma Tzeitel supposedly told him to let his first-born marry the tailor instead of the butcher.)

Though it was originating the role of Rizzo in “Grease” that made Barbeau a star, it’s “Fiddler” that’s always been her favorite musical, “because there was so much to aspire to every night.” Including, says her lifelong friend Carolyn Mignini, who played a villager named Sima in the original production, “letting go as a way of loving.”

The show gave Rosalind Harris, who describes her 19-year-old self as a “shy country girl from White Plains,” a sense of belonging in the theater: “As a young actress I often did find it hard to be a Semitic-looking Jew,” repeatedly told she was “very gifted, though a little too special for our show.” Fiddler showed her that “there was a place for me after all, a place called Anatevka.”

As Tzeitel, “I got to be who I didn’t get to be in my own family. I got to play this girl who stood up for herself.” And as a result, she eventually became that woman: “You take a role and think you’re hiding behind it, but there’s an aspect of that character that is you.”

Entwined with history

“They knew exactly what they were after’’ in casting the show, said Turque-Marre. But not according to Harnick, the show’s 90-year-old lyricist, who sang a heart-exploding rendition of Tev­ye’s “Do You Love Me?” with Andrea Martin as his wife, Golde, at the benefit.

Asked what, exactly, they had been looking for, he laughed and said, “The same thing you’re always looking for — a fine actress with a fine voice, somebody who looked like they could be Jewish, but even that wasn’t that important, and somebody relatively attractive.” (That “relatively” almost made Turque-Marre spit out her wine, but she did laugh. And speaking of relatives, she is my aunt by marriage.)

Merlin, who’d already played opposite Laurence Olivier in “Becket” pre-Fiddler, met producer Hal Prince through the show. And as a result, she went on to become casting director for Stephen Sondheim musicals including “Company,” “A Little Night Music,” “Follies,” and “Sweeney Todd.” A longtime proponent of nontraditional casting, Merlin always felt, she said, that the strength of the casting for “Fiddler” was actually in its diversity.

The day she herself was cast for the show was Nov. 22, 1963, so when she came out of the theater, people who had just learned that President John F. Kennedy had been shot were “running down the street and screaming.”

When the show opened at the Imperial Theatre on Sept. 22 in 1964, the same year the Civil Rights Act passed, so much was changing in American life that it seemed the perfect moment for a show about the attempt to hold on to faith and tradition amid prejudice and upheaval, but that’s also been the case ever since. And when mamas, papas, sons and daughters are no longer a source of humor, heartbreak and constantly moving “red lines,” the show will have lost its appeal.

Harnick jokes that when his own mother saw the original production, her only comment was that it was “very nice.” Then he took her backstage to meet Zero Mostel, who originated the role of Tevye, and “she said, ‘You know my son was married to Elaine May.’ That’s what she thought was important!”

In November, Molly Smith will direct “Fiddler” at Arena Stage. Next year, the show may get its fifth Broadway revival, directed by Bartlett Sher and produced by Jeffrey Richards and Jerry Frankel. And with luck and an angel or two, the National Yiddish Theatre, which brought so many of the show’s alums together last week, will get to celebrate its 100th birthday.