Sylvia Horowitz could have been a mighty suffragette, but she was born to non-religious working-class parents in 1919, a year before women won the vote. After that, she didn’t waste a single year, which altogether amounted to a total of 101.

She was enrolled at Girls Commercial High School, in Brooklyn, to learn trades suitable to women, but she swore off typewriting in favor of art, so she and classmates practiced life drawing by posing nude in Sylvia’s tenement bedroom. A favored model was classmate Edythe Marrenner, who became Susan Hayward (pity about the name change). Sylvia’s baby brother, Bob (later an electronics genius who pioneered cable television and perfected the dot-matrix and color printers), was entrepreneurial even at age 10. He charged friends five cents to peek over the transom; the price was double that if Edythe was posing. Fifty years later, the elegant but never vain Sylvia went topless on an Italian beach after her first mastectomy, just to keep her daughter company.

Sylvia moved on to fabric design. One of her creations was stitched into a gown for Eleanor Roosevelt, whom she met after winning first prize at age 15 in a poster contest at the height of the Depression for the annual Brooklyn Free Milk Fund. They remained friends for the rest of the First Lady’s life.

She didn’t waste a single year, which altogether amounted to a total of 101.

By 1935, her family had changed their last name to Howard. (Jews hoped to fly under the radar of Father Coughlin.) Still in her teens, Sylvia traveled the world as a highly paid designer and stylist in the fashion industry, even creating the packaging for Fabergé Tigress perfume. Her fiancé was a handsome pilot, Richard Decker. In 1939, and only 23 years old, he set out in a monoplane, determined to cross the Atlantic and fly to Palestine to aid Jewish refugees and the Jewish Brigade there. Decker vanished into the ocean.

The early 1940s brought her Irving, a wealthy suitor, but instead she eloped with Murray Fuhrman, a dapper, Brooklyn-born, St. Andrews–trained radiologist, who had organized British medical units to fight Fascists in Spain and was nearly executed on one occasion. Murray was a catch, and at least one mother in the neighborhood who had hoped to land him for her daughter gossiped to Murray’s Orthodox parents that Sylvia was a shiksa. Sylvia was a green-eyed platinum blonde, with no hint of the shtetl about her. Nonetheless, the dismayed parents said nothing when she was introduced. Months later, the parents were speaking in Yiddish, and she joined in. The world had not ended. Four years after that, Sylvia and Murray welcomed their daughter, Leni.

Doctors had warned Sylvia not to marry Murray, since he was succumbing to acute malignant hypertension, a disease that had killed his mother in her 40s. At 34, he had been given only six months to live. Undaunted, Sylvia located Dr. Walter Kempner at Duke University, who had formulated his “rice diet,” severely restricting salt and animal fat. Murray recovered, and thanks to Sylvia’s cooking him three meals a day on this strict regimen, lived to be 82.

Horowitz greeting R.A.F. pilots in New York City.

Living with her family in Queens, Sylvia became the first woman to head the Kew Gardens Civic Association. The local newspaper reported: “Unlike some women, she only talks when she has something to say.” On occasion, this formidable community leader could defer to her husband as “Mrs. Murray Fuhrman.” Her formal education had ended at high school.

In 1956, after enrolling Leni in the United Nations International School (UNIS), Sylvia attracted attention with her fine shrimp salad at a school benefit, and after 1967, when U Thant appointed her special representative of the secretary-general (a post that she would hold under six secretaries-general, until her retirement at age 91), she began fundraising and lobbying city government for a new building on a landfill in the East River. She opted for a salary of $1 a year. Murray hadn’t wanted his wife to “work,” even though when they met she had been earning three times his salary. Yet she quit work to be a reluctant housewife.

In 1969, British jet pilots participated in an international air race across the Atlantic, to touch down in New York, and then check in at the top of the Empire State Building. Sylvia arranged for one of the planes, a so-called Harrier Jump Jet, to make a vertical landing on her new building plot on the East River landfill. It was one of the first times a military jet landed in a city center, allowing the Harrier pilot, Tom Lecky-Thompson, to win the race. British Aerospace technology and Sylvia both scored a publicity coup.

The U.N. school’s offerings expanded through the 1970s, creating what was among the first international-baccalaureate programs in the United States. Sylvia spearheaded the UNIS Development Fund, organized fundraisers, including a performance by the Bolshoi Ballet, a stamp auction, and even commissioned a stamp designed by Pablo Picasso, the sale of which went to benefit UNIS. Brother Bob Howard, now a full-fledged tycoon, donated a million dollars for the auditorium.

U Thant assigned her to commission an anthem for the United Nations, which she accomplished with an unlikely pairing of Pablo Casals and W. H. Auden. It premiered in 1971 in the General Assembly Hall. Casals became a great friend and houseguest of the Fuhrmans, a friendship that lasted until his death, in 1973 at age 96. Don Pablo’s widow, Marta, and pianist Eugene Istomin were married a few years later at Sylvia’s house, which became home to many—some of whom had lost theirs.

No friendships were more enduring, though, than those of Kofi Annan and his wife, Nane. Kofi commissioned Leni to design a Messenger of Peace pin, awarded by him to honorees including Jane Goodall, Yo-Yo Ma, and Muhammad Ali. Kofi flew to New York from Geneva to celebrate Sylvia’s 90th birthday.

Shortly after graduation from Carleton College in 1970, Leni met a fellow at a Halloween party thrown by Sylvia’s Filipina secretary, then moved in with him three days later. After 10 years, they decided to get married. Sylvia’s response: “I didn’t know you were so square.” Both she and Murray were delighted. She was not your average Jewish mother-in-law. She was extraordinary and she was mine, for 50 years.

Charles DeFanti is a New York–based writer