The original Little House books were a series of eight autobiographical children's novels written by Laura Ingalls Wilder and published by Harper & Brothers from 1932 to 1943. The eighth book, These Happy Golden Years, featured Laura Ingalls at ages 15 to 18 and was originally published with one page at the end containing the note, "The end of the Little House books." The ninth and last novel written by Ingalls Wilder, The First Four Years was published posthumously and unfinished in 1971. Although her intentions are unknown, it is commonly considered part of the Little House series and is included in the 9-volume paperback box set Little House, Big Adventure (Harper Trophy, May 1994).
Several book series and some single novels by other writers have been published for children, young adults and adult readers. They provide fictionalized accounts of the lives of Wilder's great-grandmother Martha Morse Tucker, grandmother Charlotte Tucker Quiner, mother Caroline Ingalls, and daughter Rose Wilder Lane's childhood and teenage years, as well as Wilder's own missing years—those portions of her life not featured in her novels, including most of her adult life. One story not written by Wilder is Old Town in the Green Groves. It is the "lost little house" years.
In addition, simplified versions of the original series have been published for younger children in chapter and picture book form.
Some nonfiction books by Ingalls Wilder, and some by other writers, are sometimes called Little House books or Little House on the Prairie books.
The eight Little House books published during the author's lifetime are public domain in countries where the term of copyright lasts 50 years or less after the death of the author.
The story of the first book in the series, Little House in the Big Woods, revolves around the life of the Ingalls family in their small home near Pepin, Wisconsin. The family includes mother Caroline Lake Quiner Ingalls, father Charles Phillip Ingalls, eldest daughter Mary Amelia Ingalls, middle daughter (and protagonist) Laura Elizabeth Ingalls Wilder, and youngest sister Caroline Celestia "Carrie" Ingalls Swanzey. Although Laura turns five years old during the book, the author was actually only three years old during the real-life events documented in the novel. According to a letter from Wilder's daughter, Rose, to biographer William Anderson, the publisher had Laura change her age in the book because it seemed unrealistic for a three-year-old to have such specific memories. For the sake of continuity, in Wilder's later book, Little House on the Prairie, Laura portrayed herself as between six and seven years of age.