The ties between Loudoun County and the American Civil War go back to the county's involvement in the suppression of John Brown's raid on Harpers Ferry in 1859. On June 9, Colonel Thomas Jonathan Jackson (later known as “Stonewall” Jackson) ordered that the bridges at the top of Loudoun County be burned. Up to that point, Loudoun had been a Whig stronghold and had stood firm in favor of preserving the Union. When citizens of western Virginia refused to secede and formed West Virginia, Loudoun found itself in a precarious position of bordering two states that remained with the Union. During the Civil War, Colonel John Mosby and his rangers were active in Loudoun County, and it was also home to the Laurel Brigade, a famous Confederate cavalry unit led by Elijah V.
Loudoun County experienced more hardship during the Civil War than any other Virginia county where no major battle was fought. Four major road systems crossed Loudoun from east to west, connecting it to Fairfax County and other counties in Virginia and West Virginia. Located on Virginia's northern border, Loudoun County became a border area after Virginia seceded from the Union in 1861. At a meeting, nine prominent citizens were elected to draft a preamble and resolutions on the county's stance in the crisis. Joseph Hooker began pursuing Lee and entered Loudoun County on June 17, heading to Edwards Ferry where pontoons had been mounted. Lee sent John Bell Hood and George Pickett's divisions east of the Blue Ridge Mountains through Loudoun County to protect the mountain passes and guard his right flank. The Rangers often visited Pickett's Public House, now part of the Loudoun County court complex.
In addition to road transport, Loudoun was also the terminus of the Alexandria, Loudoun and Hampshire Railroad. The low ridge stretches across the county from Leesburg to Aldie, where it meets Bull Run Mountain on the border between Loudoun and Prince William County. It has been said that no Virginia county that has not seen a decisive battle suffered more than Loudoun. Loudoun was one of twelve counties and three cities represented (those under nominal federal control). The Potomac Greys (Company H, 8th Virginia Infantry) and the Leesburg Cavalry (Company K, 6th Virginia Cavalry) were mainly from Leesburg, while the Loudoun Artillery and the Loudoun Guard (Company C, 17th Virginia Infantry) recruited men from all over Loudoun County. The professional soldier was not attractive to most of Loudoun's men, so only four regiments were created.