During the Civil War, Judge Richard Parker's 1,120-acre plantation, including the 195 acres that now comprise the River Campus, stood near Snickers Gap, a gateway into the Shenandoah Valley frequently used by Union and Confederate armies. Parker, known for presiding over John Brown's trial in the autumn of 1859, owned the property and spent time at the Retreat, though his primary residence was in Winchester. The property figured significantly in the Battle of Cool Spring, the largest and bloodiest battle fought in Clarke County, in which elements of Confederate general Jubal Early's command fought a contingent of Union forces led by Gen. Horatio G. Wright. Altogether 13,000 Union and Confederate troops fought there, and the Confederate victory resulted in more than 800 casualties. On the afternoon of July 18, 1864, approximately 5,000 Union soldiers commanded by Col. Joseph Thoburn marched across Parker's property and crossed the Shenandoah River, while three Union artillery batteries deployed on the heights in the battle's final phase. Afterward, exhausted and wounded Union soldiers sought safety on this side of the Shenandoah, and during the night of July 18 and into the following morning troops from the 2nd Rhode Island Infantry picketed the river's eastern bank and provided cover for wounded Union soldiers escaping to this side.