This is a very detailed and referenced documentary of the development of an amazing service, the telegraph. Although many of the details would not interest most people, including me; for example the details of how the inventions progressed and the minutia about how the machines worked.
However, I think everyone would be interested in the vastness of the system, how "portable" it was (e.g. telegraph operators would accompany generals in the Civil War and tap into wires to send information back to headquarters or the President), and how early it was up and running in the history of our country. The first message was sent two years before the Mormon pioneers left Nauvoo for the west (1844)!