I find the history of the Boxcar Children series to be quite interesting. The author, Gertrude Chandler Warner, wrote the first book in the 1920's, for one of her classes. It's designed to help children how to read, with simple words and a easy-to-follow story.
The book got reissued in the 40's, which prompted her to write a sequel. She wrote a new book in the series every 1-5 years until she died in the 70's. I'm kind of surprised it took her so long to write these books, considering how simple the stories are. They're classified as mysteries, but that's debatable, in my opinion. Some of the books are clearly just "the Alden family has a fun time", with a 2-3 chapter mystery slapped onto it.
From what I can tell, she didn't think of it as the Boxcar Children series. She thought of it as the "Alden Family Mysteries". That's the name which is on the inside of the older editions. That name makes way more sense, considering there are no boxcars in the series, outside of the first book. There are also no numbers on the older editions; the books are listed in order, but not numbered.
The books are owned by Albert Whitman, but in the 90's, they partnered with Scholastic Publishing. Together, they turned it into a full-blown series, which has published about four books a year, ever since. The name changed to "Boxcar Children", the characters were modernized, and it became a standard mystery series. That is, the mystery is always the focus, there's always four suspects, always three suspects, and so on. If I had enough time, I could probably figure out the series formula. Book #35 is the only book I've read from the ghostwritten series.