Although I expect that this series was designed for mid-grade school, my younger children have still found it to be very interesting for read-alouds. The story of the Pony Express tends to be one of rather high interest for young children, but one that is given very brief mention in most history textbooks. I found it very interesting to discover that the Pony Express only ran for a year and a half, how it was affected by the California Gold Rush and the Civil War and how it paved the way for running of telegraph lines coast to coast which made the service obsolete. Several rather colorful figures, including Buffalo Bill and Wild Bill Hickok worked for the Pony Express and Mark Twain wrote about his brief encounter with a Pony Express rider while journeying on a stagecoach.
Various editions available