Signal Corps in the American Civil War

The Signal Corps in the American Civil War comprised two organizations: the U.S. Army Signal Corps, which began with the appointment of Major Albert J. Myer as its first signal officer just before the war and remains an entity to this day, and the Confederate States Army Signal Corps, a much smaller group of officers and men, using similar organizations and techniques as their Union opponents. Both accomplished tactical and strategic communications for the warring armies, including electromagnetic telegraphy and aerial telegraphy ("wig-wag" signaling). Although both services had an implicit mission of battlefield observation, intelligence gathering, and artillery fire direction from their elevated signal stations, the Confederate Signal Corps also included an explicit espionage function.

The Union Signal Corps, although effective on the battlefield, suffered from political disputes in Washington, D.C., particularly in its rivalry with the civilian-led U.S. Military Telegraph Corps. Myer was relieved of his duties as chief signal officer by Secretary of War Edwin M. Stanton for his attempts to control all electromagnetic telegraphy within the Signal Corps. He was not restored to his role as chief signal officer until after the war.

The "father" of the U.S. Army Signal Corps was Major Albert J. Myer, an Army surgeon with an interest in communications by sign language for the deaf and then in signaling over long distances with lightweight and simple to use equipment. He invented a signaling system using a flag (or a kerosene torch for nighttime use) that is known as wig-wag signaling, or aerial telegraphy. Unlike semaphore flag signaling, which employed two flags, Signal wig-wag required only one, using a binary code to represent each letter of the alphabet or digit. Myer was serving at Fort Duncan, Texas, in 1856 when he wrote to Secretary of War Jefferson Davis and offered his signaling system to the War Department. Although the chief engineer of the Army, Colonel Joseph G. Totten, supported Myer's proposal, it did not include specific technical details and Davis rejected it. When John B. Floyd replaced Davis as secretary of war in 1857, Totten reintroduced Myer's proposal, and in March 1859, a board of examination was formed in Washington, D.C. The board, presided over by Lt. Col. Robert E. Lee, was not enthusiastic about the proposal, judging it suitable only as a secondary means of communications over short distances, but it did recommend further testing.

...
Wikipedia