Oct 11, 2014 · Tracking the Confederates. — Gettysburg Campaign —. During the Civil War, signal stations served as early warning posts, observation points, and communication centers. On June 19, 1863, 10,000-15,000 Union troops commanded by Gen. John Fullerton Reynolds, I Corps, Army of the Potomac, marched along the Alexandria, Loudoun & Hampsire Railroad from Herndon here to Guilford Station.