During the Antietam Campaign, the U.S. Signal Corps used the stone structure as a signal station. On July 4, 1827, citizens of the town of Boonsboro paraded to the top of the mountain here and began building the first monument in the country completed in honor of George Washington. On September 14, 1862, as Confederate Gen. Robert E. Lee and his staff entered Boonsboro during the Battle of South Mountain, Lt. Col. E.P. Alexander observed “a small party of people on what seemed to be some sort of tower on the mountain top.” Thinking they were Union signalers, Alexander led a squad of eight men up to investigate, but found only local citizens trying to get a better view of the combat. Federal signalmen did use the monument afterward, however, and during the Battle of Antietam three days later. The two armies revisited this valley in 1863 during the Confederate retreat after the Battle of Gettysburg, sparring across Washington County from July 5 through 14 and fighting at Boonsboro, Funkstown, and Hagerstown.