Why was The First Four Years not published until after Laura’s death?

“The First Four Years” is considered by some to be the final book in the Little House book series and box sets include this final book in them.  However, this book was not published until many years after Laura’s death.

The First Four Years was written by Wilder around 1940, but it is not clear if it was meant to be a ninth Little House book or if its intended audience was for adults.  The book was much more adult oriented than any of her previous books, including the previous last book of the series, These Happy Golden Years – a book which originally ended with “The end of the Little House books” when it was first published in 1943.

The manuscript for The First Four Years was discovered among Wilder’s papers after her death, but Rose Wilder Lane never did any editing to the manuscript after it came into her possession.  However, it is unknown why Rose never did editing work on it, as she did for the rest of the Little House book series. When Rose passed away in 1968, Roger Lea MacBride inherited the estate and discovered the manuscript and the book was finally published in 1971 exactly as Laura wrote it, aside from minor spelling corrections.