Fort Ethan Allen was a repeating station, transmitting messages back and forth to other nearby stations.
A series of signal stations linked the forts of the Defenses of Washington. The soldiers who relayed secret messages from station to station had to learn new code systems. To communicate, they waved flags, blinked lights, set of rocket flares, or where wires had been strung, sent telegrams. In 1863, U.S. Army records listed 70 signal stations.
"It was a repeating station in every sense of the word. I gradually opened with other stations until the number of directly communicating was six. This compelled me to destroy the beauty of the large chestnut . . ."
Lieutenant Willlard Brown, 1864
Members of the Signal Corps, 1861
Each Union signal officer was issued a set of seven flags in red, black, and white, each with a contrasting center square.
Signal Tower, 1865
Stripped of its top and branches, a large chestnut tree served as a base for Fort Ethan Allen's signal tower. The house at the base of the tree, which housed the fort's commanding officer became the residence of the superior signal officer and finally the signal station. No trace of the signal tower remains.
A First in American Warfare
On September 24, 1861, Thaddeus S. C. Lowe, Chief of the Corps of Aeronautics of the U.S. Army, launched a balloon from Fort Corcoran to direct artillery artillery fire on Confederate soldiers three miles away in Falls Church. From the balloon, Lowe signaled firing instructions to soldiers on the ground. They, in turn, relayed messages to gunners at Fort Ethan Allen. For the first time in warfare, gunners could accurately fire on an enemy they could not see. This was the only offensive attack on Confederate troops from an Arlington fort.
Army in the Air
Lowe, who was personally appointed by President Lincoln to head the army's Balloon Corps, commanded seven balloons and eight aeronauts. In the photos from left to right: operators fill the balloon Intrepid using portable hydrogen generators; replenish Intrepid with air from Constitution; and hold tether lines as Lowe (aloft) surveys enemy positions during the Peninsula Campaign near Williamsburg, Virginia in May 1862. The corps was disbanded in 1863.