Thoroughfare Gap is a water gap in the Bull Run Mountains created by Broad Run between High Point Mountain to the north and Bisquit Mountain to the south. It is located in Fauquier County and Prince William County, Virginia. Interstate 66, Virginia State Route 55 and the Manassas Gap Railroad pass through the gap. The ruins of historic Beverley Mill are located at the gap.

The gap was the site of the August 28, 1862, Battle of Thoroughfare Gap (also referred to as Chapman’s Mill) during the Northern Virginia Campaign (June-September 1862) of the American Civil War. Principal Commanders were Brigadier General James Ricketts for the north and Lt. General James Longstreet for the Confederates. Casualties were estimated at 100.

“After skirmishing near Chapman’s Mill in Thoroughfare Gap, Brig. Gen. James Ricketts’s Union division was flanked by a Confederate column passing through Hopewell Gap several miles to the north and by troops securing the high ground at Thoroughfare Gap. Ricketts retired, and Longstreet’s wing of the army marched through the gap to join Jackson. This seemingly inconsequential action virtually ensured Pope’s defeat during the battles of Aug. 29-30 because it allowed the two wings of Lee’s army to unite on the Manassas battlefield. Ricketts withdrew via Gainesville to Manassas Junction.” (http://www.nps.gov/hps/abpp/battles/va025.htm)

Result(s): Confederate victory

Sources:
http://www.nps.gov/hps/abpp/battles/va025.htm
http://en.wikipedia.org/wiki/Thoroughfare_Gap_(Bull_Run_Mountain)