Her son John MacLachlan confirmed her death but did not cite a cause.
Mrs. MacLachlan wrote more than 60 children’s books during her half-century career, which she began in her mid-30s after her own children started school, leaving her time in the day to collect her memories and observations and turn them into stories.
She deplored children’s books of the moralizing kind, those sledgehammers of literature wielded by grown-ups determined to pound ideas into young minds.
“Among some writers there’s this ghastly notion that one has to teach children lessons,” she once told the Orange County Register. “That’s condescending and incorrect. It’s not what writing is about. You write to find out what you’re thinking about, to find out how you feel.”
Mrs. MacLachlan’s thoughts often ran toward family and place, the two elements at the core of her most famous book, “Sarah, Plain and Tall.” The volume received the Newbery Medal, the highest award in children’s literature, and has sold more than 7 million copies since it first appeared in 1985, according to the publishing house HarperCollins.
Set at the turn of the 20th century, the book tells the story of a farmer who lost the mother of his two children in childbirth years ago and places a newspaper advertisement for a new wife. The children, Anna and Caleb Witting, correspond by letter with their would-be new mother, Sarah Wheaton, who leaves her home on the rugged coast of Maine to join them on the windswept prairie and braid Anna’s hair, bake bread and sing.
“I will come by train,” Sarah writes. “I will wear a yellow bonnet. I am plain and tall.”
The canon of children’s literature has long reserved a prominent place for the prairie, which was most famously evoked by Laura Ingalls Wilder in her celebrated series about the “little house” that was home to her pioneer family. Mrs. MacLachlan, who spent the early years of her childhood on the prairie of Wyoming, was credited with making a proud installation in that tradition.
“The 58-page book, accessible to early readers, perfect for reading aloud, poignant and affecting even to jaded teenagers and weary adults, is, as a New York Times reviewer [observed]’the simplest of love stories expressed in the simplest of prose,’” Eden Ross Lipson, the Times’s children’s book editor, wrote when “Sarah, Plain and Tall” received the Newbery Medal in 1986.
Mrs. MacLachlan said that the book was inspired by a story her mother had told her about a “wonderful woman who came into the family” as a mail-order bride.
“Can you imagine how very brave and courageous she must have been?” the author remarked to an interviewer. “What if she did not like the children? What if she did not like the man? What if they didn’t like her?
“Sarah, Plain and Tall” was adapted into a widely viewed 1991 Hallmark Hall of Fame TV movie starring Glenn Close as Sarah and Christopher Walken as Jacob Witting, the father of Anna and Caleb. Mrs. MacLachlan co-authored the script.
She wrote several sequels to the book, including “Skylark” (1994), “Caleb’s Story” (2001), “More Perfect Than the Moon” (2004) and “Grandfather’s Dance” (2006). Walken and Close reprized their roles in a Hallmark Hall of Fame version of “Skylark.”
Several other novels by Mrs. MacLachlan were adapted for TV, among them “Journey” (1991), about a boy whose mother abandons him to be raised by his grandparents, and “Baby” (1993), about a foundling and the wounded family that takes her in.
Many of Mrs. MacLachlan’s works contained autobiographical elements. In her novel “Cassie Binegar” (1982), the protagonist often listens to adult conversations while hiding on the floor underneath a tablecloth. Mrs. MacLachlan had done the same as a girl. When her mother de ella read the manuscript of the novel, she sent Mrs. MacLachlan the floral fabric that had covered their family’s dining room de ella.
“I never knew my mother knew,” Mrs. MacLachlan said.
Patricia Marie Pritzkau, an only child, was born in Cheyenne, Wyo., on March 3, 1938. Her father was a philosophy professor, and her mother was a homemaker who had been an English teacher.
“My professor father made sure I never forgot about the connection of books and life,” Mrs. MacLachlan wrote in a reflection published in The Washington Post in 2004. “Every single day we acted out books and stories. I remember Peter Rabbit most vividly. My father would play a fierce Mr. McGregor, ‘scritch scratching’ in the garden of the living room, and I’d play a frightened Peter Rabbit, running into the safety of the coat closet. Even today, when I open a coat closet, I get goose bumps on my arms, remembering how it was to be zipped into the fur of Peter Rabbit.”
Her mother, she recalled, devotedly accompanied her on jaunts to the library and set places at the dinner table for Mrs. MacLachlan’s imaginary friends.
Once, a teacher, unimpressed by a story that the young Mrs. MacLachlan had composed, declared that she would never be a writer. The insult stung but was outweighed in its impact on her by the love of her parents and their unceasing efforts on her to cultivate her imagination on her.
“Children read with a certain belief and vision about finding themselves in literature,” Mrs. MacLachlan said when she received a 2002 National Humanities Medal, explaining the mind-set that she brought to her writing. “Literature changes their lives. They have a sense of closeness with literature that speaks for them.”
Mrs. MacLachlan was in elementary school when her family relocated to Minnesota. They later moved east when her father became an administrator at the University of Connecticut, where Mrs. MacLachlan received a bachelor’s degree in English in 1962.
She married that year and worked for a family services agency before beginning her writing career. Her first volume of hers, “The Sick Day,” was a picture book published in 1979.
Mrs. MacLachlan’s first novel was “Arthur, for the Very First Time” (1980), about a boy and the summer he spends on a farm with his amusingly odd aunt and uncle. Her 1988 novel, “The Facts and Fictions of Minna Pratt,” centered on a young girl and her longing for the attention of her writer mother.
Mrs. MacLachlan wrote several books with her daughter, Emily MacLachlan Charest, including “Once I Ate a Pie” (2006), “Fiona Loves the Night” (2007), “I Didn’t Do It” (2010), “Cat Talk” (2013) and “Little Robot Alone” (2018).
Mrs. MacLachlan’s husband of 53 years, Robert MacLachlan, died in 2015. Besides her son, of Williamsburg, survivors include her daughter, of Stow, Mass.; another son, Jamison MacLachlan of Plymouth, Mass.; and six grandchildren.
Such was Mrs. MacLachlan’s connection to the Wyoming of her youth — and to the world of “Sarah, Plain and Tall” — that throughout her life, she kept a souvenir of the prairie.
“I carry a small bag of prairie dirt to remind me of where I began — the prairie that I miss and still dream about,” she said in an interview published on the Two Writing Teachers website. “It is sort of like a charm from my childhood. I had a wonderful childhood with wonderful parents who were storytellers and educators. They loved and respected children. So, my little bag of prairie reminds me of them, too.”