During the Civil War, Poolesville became the busiest military crossroads in Montgomery County, with more soldiers passing through than any other town there. At the intersection of two main roads and near several fords and ferries across the Potomac, the town of more than 300 people had prospered until its strategic position made it an epicenter of war. Union forces occupied the town through most of the war, and 15,000 infantry, artillery, and cavalry troops were encamped nearby in August 1861. In the fall of 1862, residents with southern sympathies hurried to nearby White's Ford to welcome Confederate Gen. Jeb Stuart's forces as they moved toward the Battle of Antietam. A few days later, on September 5, a running cavalry engagement swept through town and led to the capture of 48 Union troopers. In June 1863, war returned when the Army of the Potomac used Poolesville as a temporary headquarters while marching toward Gettysburg. The John Poole House, built in 1793 by John Poole Jr., stood through these events. It served as a trading post and later a post office for the surrounding countryside. In 1820 it was one of only four buildings in town, and by the mid-19th century Poolesville had become the second largest settlement in Montgomery County.