At Thoroughfare Gap in the Bull Run Mountains between Mother Leathercoat Mountain and Pond Mountain, Brig. Gen. James Ricketts's Union division was flanked during the Battle of Thoroughfare Gap by a Confederate column passing through Hopewell Gap several miles to the north and by troops securing the high ground at Thoroughfare Gap. The gap long served as a passage for water, road, and rail, and before that for migrating buffalo and traveling American Indians, later becoming a transportation corridor for grain and goods between the Shenandoah Valley and the Atlantic and a strategic wartime passage during the French and Indian, Revolutionary, and Civil Wars. Chapman's Mill, built in 1742 near the gap, became a prosperous gristmill that helped foster the Shenandoah Valley as a wheat- and corn-producing region for the next one hundred years. The Battle of Thoroughfare Gap, also known as the Battle of Chapman's Mill, took place in Fauquier and Prince William Counties on August 28, 1862, and though it was a small engagement with only about 100 combined casualties, it had immense strategic significance because the failure of Union troops to stop the advance of Confederate Lt. Gen. James Longstreet virtually ensured the defeat of the Union Army at the Second Battle of Manassas, spurred the Confederacy to invade Maryland, and ultimately led toward the Battle of Antietam. During the war, Chapman's Mill was turned into a Confederate meat-curing warehouse and distribution center, where herds of cattle and pigs were enclosed in large pens and more than two million pounds of Confederate meat were stored, before Confederates leaving after the First Battle of Manassas burned the meat and the mill to keep them from advancing troops; the charred walls still stand beside this major east-west thoroughfare.
