Betsy Byars, the author of “The Summer of the Swans” and other prizewinning works of children’s literature drawn from the real world, with heroes and heroines who survive their lonely, sometimes broken existence by caring for one another, died Feb. 26 at her home in Seneca, S.C. She was 91.

She had complications from a fall, said her daughter Nan Byars.

Mrs. Byars wrote more than 60 books for those in-between children too young to be called big and too old to be called small. In her selection of subject matter, she abided by the old writer’s dictum to write what one knows, which meant no wizards or vampires but also no shortage of fear or triumph.

“I take some kids and throw them into a crisis and solve the crisis,” Mrs. Byars once told the Mini Page, a syndicated newspaper supplement for children, although she might have said with equal honesty that the children solve the crises themselves.

Among her best-known works was “The Summer of the Swans” (1970), which received the Newbery Medal for excellence in children’s literature. The novel centers on 14-year-old Sara, who reports that “the peak of my whole life so far was in third grade when I got to be milk monitor.”

Since their mother’s death, she and her two siblings — a beautiful older sister and a younger brother who is intellectually disabled — have lived with an aunt in West Virginia. Captivated by the swans at a nearby lake, Sara’s brother, Charlie, leaves the house one night and becomes lost in the woods. In her ultimate act of devotion, Sara finds Charlie, proving her mettle not only to the reader but also to herself.

“Betsy Byars has a gift for exposing the soul of the lost child — the damaged, the alienated, the unloved,” children’s author Marilyn Kaye wrote in a New York Times review of another book by Mrs. Byars, “The Glory Girl” (1983).

Like many of Mrs. Byars’s books, “The Summer of the Swans” was based at least in part on real life. As a volunteer tutor, Mrs. Byars had formed meaningful relationships with children with intellectual disabilities. Charlie was “not one of the children,” she said in her Newbery acceptance speech, but “the book would never have been written if I had not come to know the children I was tutoring.”

Mrs. Byars said that after “The Summer of the Swans” received the Newbery, she had to install a larger mailbox to accommodate all the letters from young readers and other inquiries she received. No work, she reported, elicited more mail than “The Pinballs” (1977), a novel about three children — Carlie, Thomas J and Harvey, called “pinballs” for what seems to be their destiny to bounce around — who are placed together in a foster home.

In “The Night Swimmers” (1980), a young girl, Retta, cares for her two brothers after their mother dies and their father takes to the road as a country singer. The children seek fun — but also court mortal danger — with clandestine nighttime swims in a wealthier neighbor’s yard. Mrs. Byars said that the novel, which received a National Book Award, was inspired by a friend who worried about the neighbor children who let themselves into her pool when she was away.

Mrs. Byars received an Edgar Award from the Mystery Writers of America for her novel “Wanted . . . Mud Blossom” (1991), one of several books about the Blossom children, whose mother travels the rodeo circuit where their father was killed by a steer. Mud is the family dog, and his misadventures were inspired in part by those of Mrs. Byars’s childhood dog Mac, who was “wanted” for the murder of a chicken.

She said the book she most cherished was “The Midnight Fox” (1968), about a boy, Tommy, and the love he develops for a black fox while spending a lonely summer on his aunt and uncle’s farm. It was her first book that included elements of her life, Mrs. Byars said, and the first that “turned out the way I had hoped it would.”

“I sometimes think my books are like scrapbooks of my life,” she wrote on her website, “because almost every incident brings back a memory.

Betsy Alice Cromer was born in Charlotte on Aug. 7, 1928. Her father was a textile executive, and her mother was a homemaker.

She said she did not aspire to be a writer when she was growing up. “I had never even seen one,” she wrote in a memoir, “The Moon and I” (1991), “but their photographs looked funny, as if they’d been taken to a taxidermist and stuffed.”

“This corpselike look, I figured, came from sitting alone all day in a room typing, which couldn’t be good for you,” she continued. “I was glad there were people willing to do this. I loved books and didn’t want them to become extinct. But I cared too much about myself and my future to consider becoming one.”

She set out to follow her older sister as a math major in college but, deterred by a calculus class, instead received a bachelor’s degree in English from what is now Queens University of Charlotte in 1950.

The same year, she married Edward Ford Byars. In addition to her husband, of Seneca, survivors include four children, Laurie Myers of Augusta, Ga., and Betsy Duffey of Atlanta, who write together as the Writing Sisters; Nan Byars of Charlotte; and Guy Ford Byars of Cincinnati; nine grandchildren; and nine great-grandchildren.

Mrs. Byars’s earliest published writings were short articles for women’s magazines and publications including the Saturday Evening Post. She began writing children’s literature as her own children grew up, and she endured repeated setbacks before her first book, “Clementine,” was published in 1962, after being rejected by numerous publishers.

By that time, the Byars family had moved to Morgantown, W.Va., where Mrs. Byars’s husband taught at West Virginia University. She enrolled in a course about children’s literature, later describing it as “one of the turning points in my career.”

“For the first time I saw the realistic children’s novel,” she observed in comments for the Something About the Author Autobiography Series. “There had not been any of those when I was growing up. . . . I had never even considered anything realistic.”

Some of her most popular books were part of the Bingo Brown series. “If there is such a thing as a typical American kid, Bingo Brown is it,” author Fannie Flagg wrote in a Times review. “He is funny and bright and lovable without being precocious,” while also serving as a vehicle for “serious themes like puberty, unwanted pregnancy, changing roles for men and women in society, etc.”

Mrs. Byars and her husband were licensed pilots, and they lived on what her website described as an airstrip. “The bottom floor of their house is a hangar so they can taxi out and take off, almost from their front yard,” reads the description of their home. “The top floor of the house? Betsy’s studio!”

Her book “Coast to Coast” (1992) was about a girl, Birch, who flies across the country with her grandfather in his Piper Cub plane. Mrs. Byars said that she and her husband took the same trip, in a plane just like the grandfather’s, and that everything her characters experienced had happened to them.

“Every time I sit down to write a book, I feel like that character in the old fairy tale who, in order to survive, has to spin straw into gold,” she once told a publication called the School Librarian. “What I know about spinning straw is nil, and I have learned from hard reality that no little man in a funny suit is going to pop out of the woodwork to strike a deal.”

“We authors write the best we can, with what skills we have, what tricks we’ve learned,” she went on to say, “and then if we are lucky, very lucky, the straw actually will be turned into gold, for a fleeting moment by the miraculous mind of a child.”