During the Battle of Brandy Station, after crossing at Kelley's Ford, Col. Duffie's division headed toward Stevensburg and encountered a small Confederate force on Hansboro Ridge just east of town. Duffie's much larger command drove the Confederates back in disorder toward Norman's Mills Ford, the Mt. Run crossing for the Carolina Road, and pursued closely, but at Mt. Run the stream proved as effective a barrier as the Rappahannock River because horses could cross only at prepared crossings. At 12:30 Col. Butler and Farley, JEB Stuart's chief aide, recrossed Mt. Run as the last men to do so, and Butler remarked that the enemy was making no move against them. When Duffie found the crossing defended by a cannon and by riflemen protected in a trench formed from an 1815 canal built to power a sawmill, he chose not to force the ford directly and instead sent a flanking force on foot downstream to find a suitable crossing and drive off the defenders. The Union flanking force crossed Mt. Run at a shallow gravel bar formed where a small stream entered it from the slopes of Hansboro Ridge, but the canal trench north of there gave Confederate riflemen a strong position and created a serious obstacle. More than 200 bullets have been recovered along the canal route, and bullets found at the crossing site confirmed where the Union men crossed. About mid-afternoon Duffie received orders from Brandy Station from Pleasanton to withdraw, retrace his route to the Peola Mill Road, and enter Brandy Station by the route Gregg had taken. He did so at once and reached Brandy Station around 4PM, only to find that Pleasanton had already stopped the fighting and was withdrawing his troops across the Rappahannock River to Remington. This small Confederate force, mostly 4th Virginia Cavalry with a few 2nd South Carolina Cavalry, had earlier been badly routed on Hansboro Ridge, but with the help of Mt. Run it kept one quarter of Pleasanton's Union cavalry from firing a single shot in the Brandy Station area. A 1994 Virginia Senate Document concluded that if Duffie had reached Brandy Station in time, the battle might not have ended effectively as a draw, and the holding action at Mt. Run probably determined the outcome of the daylong battle.
