The Civil War in the United States was a gigantic moral and physical effort that has elicited the feelings of hundreds of its participants and thousands of its students. Yet, in all of the treatment of the conflict, a dearth of information is available on the informational agencies that contributed to the Union military victory. No historian to date has chosen to publish a definitive study of these agencies and it is the hope here that some light can be shed on four types of organizations that were, for the most part, developed as a result of the war. This paper deals only with the evolution of these units, their organization and personnel, and the ways in which they carried out their duties and the devices used.
To get a clearer picture of the major organization, The United States Signal Corps, use has been made via microfilm of the letters sent from the Official of the Signal Officer, 1861 and 1862, and the original manuscript of letters written in the field by Colonel Myer during the Peninsular Campaign.
When considering this thesis one definition should be kept in mind. The term Federal military information refers to any information of a military nature, or of significance to the military, both for land army or naval use, for its operations against the Southern Confederacy
