In 1926, Edward Stratemeyer of the Stratemeyer Syndicate sketched out ideas for a series of stories featuring a girl detective. He gave the outline of the first book to a young journalist named Mildred Wirt Benson and asked her to write the corresponding novel. This later became The Secret of the Old Clock. Benson was to use the pseudonym Carolyn Keene and couldn’t claim authorship of the book. The rights were retained by the Stratemeyer Syndicate. For her efforts, Benson was paid $125 to $250 for each book she wrote, which was the equivalent of three months’ salary for a reporter at the time. She went on to pen the bulk of the first 30 books in the series.

The Secret of the Old Clock was the beginning of the 175-book franchise known as The Nancy Drew Mystery Stories. Grosset & Dunlap published the first 56 novels from 1930 to 1979. Simon & Schuster published the rest of the series, ending it in 2003. In 2004, the publisher launched an updated series called Nancy Drew: Girl Detective. This was followed by The Nancy Drew Diaries in 2013. Both spinoffs received mixed reviews and were less successful than the original series.