On the morning of August 27, 1862, six miles southwest of this location, General Robert E. Lee rested at the head of Lieutenant General James Longstreet’s corps as it marched toward Thoroughfare Gap to join Lieutenant General Thomas J. “Stonewall” Jackson’s corps near Manassas Junction at the Second Battle of Manassas. The 9th New York Cavalry, covering the left flank of Major General John Pope’s army on its march from Warrenton to Manassas, nearly overtook Lee’s position between Ada and Vernon Mills. Lee’s staff mounted quickly and formed a line to protect him, and the Federals mistook the horsemen for a Confederate cavalry column and turned away.