The Civil War
A Signal Corps station and training camp was established near Darnestown in 1861. Signaling with flags was invented by army surgeon Albert J. Meyer and first used against the Navahos in border warfare before the Civil War. Signaling with flags provided a rapid way to convey intelligence and battlefield orders.
Red Hill in Georgetown Washington D. C. served as the main headquarters and training center for the Union Signal Corps. The Corps had 300 officers and 2,500 men and one of the highest casualty rates of any unit in the Union army.
Information was relayed in a chain called "Signal Tree Lane" extending form Harper's Ferry up-river and all the way down-river to Georgetown. On a clear day signals could be seen for 10 miles, but with rain and fog, visibility was obscured, which sometimes made this an unreliable means of communication.
A New York infantry officer remembered being sent to Darnestown to attend a school of instruction: "The men had been selected with great care for their physical, as well as mental ability...Most of the Twenty-eighth will remember the 'Chestnut-tree station' on the Magruder farm near Darnestown, it was picturesque. The upper limbs sustained a platform for the man to wave his flag, while just underneath was the platform for the officer, who, with his glass, kept watch of the communicating station. These platforms were some forty or fifty feet above the ground and were reached by rustic ladders. This was the first line of signal stations established on the Potomac. "
(sidebar)Flags & Lights
Other than the Signal Corps, the only means of wartime communication at that time was by scouts of horseback, word of mouth form local residents, observation balloons, and telegraph lines.
From towers, building tops, tall trees, and platforms, the Signal Corps used flags and telescopes during the day and flares or torches at night to send coded messages.
The wig-wag system used signal flags of white with red square centers to provide important information during the war.