The First Four Years
The ninth book in the series, The First Four Years (novel), and the final one to feature Laura as the protagonist, follows the earliest years of Laura and Almanzo's marriage.
The First Four Years derives its title from a promise Laura made to Almanzo when they became engaged. Laura did not want to be a farm wife, but she consented to try farming for three years. At the end of that time, Laura and Almanzo mutually agreed to continue for one more year, a "year of grace", in Laura's words. The book ends at the close of that fourth year, on a rather optimistic note. In reality, the continually hot, dry Dakota summers, and several other tragic events described in the book eventually drove them from their land, but they later founded a very successful fruit and dairy farm in Missouri, where they lived comfortably until their respective deaths.
Read more about this topic: List Of Little House Books