“Once upon a time, sixty years ago, a little girl lived in the Big Woods of Wisconsin, in a little gray house made of logs.”

That famous first line of “Little House in the Big Woods” introduced a family of homesteading pioneers who have become fixtures in the American imagination. The then-unknown author was Laura Ingalls Wilder, who was born 150 years ago, on Feb. 7, 1867.

Through the autobiographical characters of Laura; her strong Pa; her loving, resourceful and always optimistic Ma; her sweet younger sisters; and her experience of a “snug and safe” home life — despite hardship, isolation, wolves and bears — Wilder gave readers a story that, as her editor crowed, “no Depression could stop.” In the tradition of Jo March in “Little Women” and Dorothy in “The Wizard of Oz,” Wilder created a brave child heroine who became a beloved national ideal.

The success of the book encouraged her to keep writing, and eventually, she published eight books, ending with “These Happy Golden Years” (1943), which describes Laura’s courtship and marriage to Almanzo “Manly” Wilder at age 18. The Little House series has spanned popular and high literary culture, from mimeographed fan newsletters and online blogs to a two-volume definitive edition in the prestigious Library of America (2012). Its characters inspired the TV hit series “Little House on the Prairie,” which ran for more than 200 episodes in the 1970s and ’80s. It has been adopted by home-schoolers and translated into over 40 languages. Overall, in the 85 years since the first book was published, in 1932, the Little House series has sold more than 34 million copies.

Why were the books so popular when they appeared, and why have they endured?

During the Depression and World War II, they offered images of family protection from the storms of history: coziness, security and the simple homemade pleasures of music, holidays and crafts. Boys also read the books for exciting details of pioneer history and exact descriptions of male skills of hunting, building and self-defense. But in the 21st century, they survive for their art, their precision of language and depth of characterization.

The 150th anniversary of Wilder’s birth in 1867 is being celebrated all along the Laura Ingalls Wilder Historic Highway, in the various homesites and museums dedicated to her life, from Wisconsin to South Dakota. Devotees will gather to buy Little House bonnets, aprons, cookbooks, dolls and dolls’ clothes, as well as new editions of the books, including “The Little House in the Big Woods,” with a foreword by Laura Bush (HarperCollins). As she recalls, she discovered the novel as a girl in “the hot, arid lands of West Texas,” identified with “a brown-haired girl named Laura,” and “tried to imagine being surrounded by tall pine trees and heavy snow.” (As first lady, Bush included Wilder in a White House symposium on female writers of the West in 2002). This summer, scholars, biographers and fans will meet at the annual LauraPalooza conference and celebration in Springfield, Mo.

The life story of Laura Ingalls Wilder is a saga in itself. After her marriage, the Wilders continued to move around the country with little success and finally settled in Missouri, where she wrote articles about farm life and farm wives in local magazines and papers. Then, at 63, she decided to write down her memories of growing up as a “pioneer girl,” including stories she had heard from her father and grandparents. Through a lengthy process of rejection by editors and publishers, and determined revision, she turned the material into a story for children.

Up until 1943, Wilder insisted that every detail and anecdote came from her memory and that the books were completely autobiographical. “My series of stories,” she wrote to a reader, “are literally true, names, dates, places, every anecdote and much of the conversation are historically and actually true.” But by the 1950s, sharp readers had begun to notice historical inaccuracies, and gradually, through biographies and critical studies in the 1980s and 1990s by William Anderson and William Holtz, it became clear that the books were based on Wilder’s memories of her childhood life, but carefully constructed, fictionalized and embellished.

Most shocking to her fans was the revelation that they had been workshopped and developed in a complex partnership with her daughter, Rose Wilder Lane, a novelist, ghostwriter, biographer and editor. Wilder and Lane had kept their collaboration a secret unknown even to their editors and publishers. Moreover, this collaboration was a source of immense personal friction, as Wilder, under Lane’s tutelage, quickly developed her own skills and vision as a writer of fiction, and Lane, her own literary career foundering, increasingly resented her uncredited service.

At first, devotees angrily viewed the very suggestion of an editorial intervention as an insult to Wilder’s memory. But in the 21st century, the tense partnership between Wilder and Lane has emerged as one of the most gripping psychological sagas of mother-daughter literary collaboration in American literary history. Most fully documented and analyzed by Pamela Smith Hill in her biography “Laura Ingalls Wilder” (2007) and her annotated edition of Wilder’s memoir, “Pioneer Girl” (2014), this relationship is still open to interpretation.

Was Lane a generous editor, coach, typist, research assistant and publicist, or was she a ghostwriter, aggressive reviser, sneaky rival, unlicensed borrower and patronizing elitist? Hill shows that Lane contributed the key idea of a shift from first to third-person narrator, making Laura a fictional character, and the structure of a calendar year in “Little House in the Big Woods.” Wilder seems like a docile pupil of Lane’s at first, but she quickly grew in skill and confidence, insisting on her own vision, her own voice and her understanding of the personalities of her characters. As the series developed and the characters matured, the stories became darker, and the symbolism of events like the plague of locusts and the murderous blizzards of “The Long Winter” grew more disturbing. Thrashing out their themes, Wilder and Lane became creative partners who benefited professionally and psychologically from their collaboration.

Wilder began writing a timeless American fairy tale, but she ended as an artful realist. As Laura Bush notes, the stories have “captured and preserved our nation’s past for each new generation of readers.”

Elaine Showalter is the author, most recently, of “The Civil Wars of Julia Ward Howe: A Biography.”

By Laura Ingalls Wilder

HarperCollins. 224 pp. $12.99