During the Civil War, Guilford Signal Station served as an early warning post, observation point, and communication center. On June 19, 1863, 10,000—15,000 Union troops commanded by Gen. John Fullerton Reynolds of I Corps, Army of the Potomac, marched along the Alexandria, Loudoun & Hampshire Railroad from Herndon to Guilford Station. Reynolds established his headquarters at the Lanesville house, erected a signal station on the northwestern portion of the property at 442 feet, one of the highest points between Washington, D.C. and Leesburg, and ran a telegraph wire to Fairfax Court House. From here, signal officers communicated constantly with nearby stations while trying to locate Gen. Robert E. Lee’s Army of Northern Virginia. As gunfire sounded from the west, Gen. J.E.B. Stuart screened Lee’s infantry from Federal cavalry at Aldie, Middleburg, and Upperville. Lee passed through the Blue Ridge Mountain gaps into the Shenandoah Valley, but the U.S. Signal Corps detected his movement as he began his second invasion of the North. On June 24, Reynolds’ corps left in pursuit, and the two armies met on July 1 at Gettysburg, Pennsylvania, where Reynolds died in the first day’s fighting.
