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).