The Password to Larkspur Lane is the tenth volume in the Nancy Drew Mystery Stories series. It was first published in 1933 under the pseudonym Carolyn Keene. The actual author was ghostwriter Walter Karig in his third and final Nancy Drew novel and his final appearance for the Stratemeyer Syndicate. Due to Karig's death in 1956, this book and his other two Nancy Drews, as of January 1, 2007, have passed into the public domain in Canada and other countries with a life-plus-50 policy.

Walter Karig was a prolific writer, who served as a US naval captain. Karig wrote a number of works on Allied naval operations during World War II. He also wrote scripts for the television series Victory at Sea. Besides his works on naval history, Karig was a novelist, publishing under his own name, and a journalist.