Zelda Fichandler in 2005. (Lucian Perkins/The Washington Post)

If you love taking in the bra­cing air of the American theater, you have Zelda Fichandler to thank. Because she supplied the oxygen.

The dream she saw fulfilled, of a dynamic environment in which actors, playwrights and audiences could share in her passion for great drama, gave the breath of life to an art form, one that was struggling at the time that she and other visionaries, such as Margo Jones at the Dallas Theater Center in Texas, came on the scene in the early 1950s.

Under the stewardship of Fichandler and her cohorts, theater developed into something refined and earthy, serious and accessible, in parts of the country that might otherwise have remained culturally parched. Her brainchild, Washington’s Arena Stage, founded with then-­husband Tom and their colleague Edward Mangum as a for-profit enterprise, would revise its business model and enter the vanguard of the country’s nonprofit theater movement — by far the dominant creative engine today of the American theater.

On the occasion of her death Friday, at 91, we must pause and reflect on the impact this tough, perceptive, impatient, wily and ferociously dedicated woman had on the nation’s stages. It’s almost impossible, in fact, to overstate the case. Her love of plays new and old, foreign and domestic; her business savvy and reverence for talent; her devotion to actors in the in-house corps she maintained were characteristics that informed the ethos of Arena. This philosophy permeated Arena through the four pivotal decades during which she was there, from Arena’s establishment in 1950 in a converted burlesque house on Ninth Street and New York Avenue NW, until 1990, long after the company had moved to its current multi-theater Southwest Washington campus.

Indeed, Fichandler’s priorities would come to embody the values of the national theater movement itself.

“She was the mother of us all in the American theater,” is the way Molly Smith, Arena’s current artistic director, puts it.

A demanding mother, to be sure. A tenacious mother. A sometimes exasperatingly meticulous mother who treated the theater as a spiritual place, one in which, in the words of an admirer in the theater business, “the high priest was the actor.”

Audiences were her parishioners and, after entering her temple, they had to be taken care of at every turn. “She made me understand that every decision about this place — including whether the toilet paper in the bathrooms rolled down this way or that way, was an artistic decision that affected the audience’s experience,” said James C. Nicola, who worked as a budding director (among other jobs) on the staff of Arena for eight years in the 1980s, and went on to become the widely respected artistic director of the New York Theatre Workshop, birthplace of “Rent.”

Fichandler would continue to broaden her influence after her time at Arena, building the acting program at New York University’s Tisch School of the Arts into one of the most formidable in the country. But Arena and its innovative spaces — the company’s main stage, challengingly configured in the round, is named for her and Tom — remained the crowning achievements of her career. Little could she have known in the ’50s how influential the place would become and how many trails it would blaze.

With its production of “The Great White Hope,” starring James Earl Jones and Jane Alexander, for example, Arena became in 1968 one of the first nonprofit theaters to have an original production move to Broadway. It also was the first to be honored with the special Tony Award now bestowed annually on a regional theater of distinction. And Fichandler broke ground overseas, too, with the Arena plays she toured to the Soviet Union in 1973, when such cultural exchanges were virtually nonexistent.

That her theater was the first in the city in the early ’50s to ignore segregation barriers and welcome all races into its spaces affirmed Fichandler as a civil rights pioneer as well. That reputation was further burnished when she actively recruited black actors and integrated her resident acting company.

Her theater seasons were wildly ambitious, stocked with plays of both the adventurous and classic stripes, and often with a focus on raising social and political awareness: Nicola says Fichandler recounted for him the story of the death threats the Caucasian Alexander received after the December 1967 Washington opening of “Great White Hope” because of her intimacy onstage with the African American Jones.

Arena’s founder selected plays as if her mission was to convince people of the limitless horizons of the stage. If her agenda could include, as it did in 1972-1973, a production of something as austere as Thornton Wilder’s “Our Town,” directed by Alan Schneider — best known for his seminal work with Samuel Beckett — it could also encompass Swiss playwright Max Frisch’s absurdist “A Public Prosecutor Is Sick of It All.”

“It was actually pretty fantastic, progressive, cutting-edge avant-garde, kind of phantasmagorical,” recalled Douglas Wager about the latter play. As a graduate student at Boston University, he took a course with Fichandler, in which she led the class through the evolution of her concepts for “A Public Prosecutor Is Sick of It All.” The encounter was the precursor to a series of jobs at Arena, which culminated in Wager becoming Fichandler’s successor as artistic director in 1991.

Wager, who now is associate dean for theater, film and media arts at Temple University in Philadelphia, describes working with Fichandler as “a mentorship unlike anything I could possibly have wished for.”

“She ran Arena from a deeply feminine understanding of allowing people to be able to speak and contribute, but she held all of the decision-making power and was as fickle as any other person could be,” Wager said. “You knew you were working for an in­cred­ibly strong, willful, gifted individual who was also a prodigiously inspired thinker.”

For generations of playgoers, too, the company has been a proud emblem of the city’s cosmopolitan patina, a testament to the fact that beyond being the epicenter of national politics, the District has matured as an influential hub for the arts.

That’s the Fichandler legacy. As those closer to her will tell you, she may have been a skillful stage director, but her greatness resided in the incisive direction she gave to a theater and a city.

“Directing was never ever her first love,” Wager said. “She got more satisfaction from molding the image and forging the artistic culture of the company and its place in society, and in the mission of how theater becomes important to the daily life of the community.”