PORTLAND – Sarah Caldwell, hailed as the first lady of opera for her adventurous productions as longtime director of the Opera Company of Boston, died Thursday. She was 82.

Caldwell died of heart failure at Maine Medical Center, according to Jim Morgan, her longtime friend and colleague and the former manager of the Opera Company of Boston.

In more than 30 years as founder-director of the Boston company, she staged and conducted some 100 operas, ranging from baroque to avant-garde.

“Opera is everything rolled into one – music, theater, the dance, color and voices and theatrical illusions,” she told Life magazine in 1965. “Once in a while, when everything is just right, there is a moment of magic. People can live on moments of magic.”

“Whichever opera you’re working on now is your favorite,” she once said.

In 1975, she became the first woman conductor at New York’s Metropolitan Opera. In a cover story, Time magazine hailed her as “the best opera director in the United States.”

“Working day and night as her own conductor, administrative boss, stage director, talent hunter, principal researcher and fundraiser, she has become a symbol of the vigorous growth of opera in dozens of cities around the U.S.,” Time wrote. “She is also one of the great impresarios in all the American performing arts.”

She was extremely hardworking – sometimes rehearsing round the clock – and often eccentric. Profiles rarely failed to mention her nearly 300-pound heft, her tendency to lose whatever she was carrying, and the opera company’s checks, which frequently bounced.

She thought the picture a bit distorted – “the idea of a poor little match girl. Lonely. Strange. Only interested in going to libraries. It’s just so totally foreign to my nature,” she told the New York Daily News in a 1981 profile. “The stories probably make great reading if you don’t have to live with them. It did turn me into a bit of a cartoon.”

But she didn’t deny the hard work.

“Of course, I’m a fanatic,” she said. “And I’m often teased about misplacing things. I’m apt to be absent-minded about certain things. There is just so much a person can think about.”

In addition to choosing standard works such as “Carmen” and “La Boheme,” Caldwell made her artistic reputation by producing unusual operas, world premieres, American premieres and original or variant editions of familiar works.

She sought out not only major stars, but emerging singers. And she brought unique theatrical touches to the material – having Beverly Sills accompanied by a music box with a mechanical, singing bird in “Barber of Seville.”

“Her best productions were as good as anything anybody’s ever seen anywhere,” Boston Globe music critic Richard Dyer once said. “She made it all exciting while meeting the highest musical standards.”

But the company had always operated on thin ice financially; for many years it lacked a permanent home and staged its productions in theaters or college auditoriums.

Some of the unusual stagings were “not just trying to be different,” she once said. “Many of them grew out of desperate circumstances in which the stage was too small for the sets or such.”

Financial problems virtually shut the Boston company around 1990. “You know the amount of money you should have – you don’t have it. To stimulate more, you just need to perform,” Caldwell said in a 1996 article in Opera News. “What knocked us out finally was not enough money for both productions and building maintenance. It’s not that we didn’t want to do it – we couldn’t.”

“The major problem in the arts today is money,” she told U.S. News and World Report in 1979. “Unless we have a remarkable infusion of support, we will not achieve the kind of life in the arts for artists and their audiences that we ought to achieve.”

She remained active, serving in a variety of posts, including principal guest conductor of the Ural Philharmonic in Ekaterinburg, Russia, and the chief organizer of Russian-American cultural exchanges that blended ballet, chamber music, ballads and poetry from the two countries.

She also tried her hand at theater, directing a New York production of “Macbeth” in 1981.

In 1999, she was appointed a distinguished professor of music and led the opera program at the University of Arkansas at Fayetteville, the town where she grew up as a professor’s daughter. She said she would continue to travel to maintain conducting and recording commitments around the world.

When she received a National Medal of the Arts from President Clinton in January 1997, he said, “She’s come a long way from Arkansas, and I’m very proud of her.” He praised her enterprise in bringing “difficult yet beautiful operas to the stage” and developing new audiences for opera.

She was hospitalized for a month in early 2001, though officials declined to say why, citing privacy concerns. She went on unpaid leave from the university and formally retired in 2004.

She had health problems and missed New England, so in 2003 she moved to Freeport, Maine, where she shared a home with Morgan, he said.

“She was famous for taking familiar operas and making them seem new,” said Morgan, who is the director of marketing for PCA-Great Performances. “She was a very important part of the development of opera in the United States and the direction it took after World War II.”

Caldwell was born March 6, 1924, in Maryville, Mo., moving to Arkansas when she was about 12. She was a child prodigy in both music and mathematics and studied violin before turning to opera and conducting.

In a 1999 interview in the Arkansas Democrat-Gazette, she recalled studying in Boston in her 20s with choral conductor Boris Goldovsky. He told her “there was nothing to be afraid of. The fact that I didn’t know anything about opera, I hadn’t studied conducting and I knew very little about the technical aspects of the theater, didn’t matter. He said that everything was learnable.”