the valley, centered on Middleburg, settlers of English descent moving west from the Tidewater region imported slave-based plantation-style agriculture. During the antebellum period, the area became a leading center of agriculture production, particularly of wheat, oats, rye, and corn. Civil War During the Civil War, the Loudoun Valley saw considerable fighting. Owing the Valley's divided loyalties, one-time neighbors took up arms against one another in bitter partisan fighting. Unionists from the northern portion of the Valley formed the partisan Loudoun Rangers, while southern sympathizers in the southern portion joined a number of partisan Confederate units including White's Rebels and Mosby's Rangers. These units frequently engaged one another in the Valley throughout the duration of the war, most noticeably at the Fight at Waterford in 1862 when White's Rebels engaged the Loudoun Rangers for the first time. Major engagements between the regular armies also occurred in the Valley, particularly in 1862 and 1863. In November 1862, following the Battle of Antietam, Union Gen. George McClellan marched his army through the Valley in slow pursuit of the retreating Army of Northern Virginia. Confederate cavalry under Maj. Gen. J.E.B. Stuart fought a delaying action against the vanguard of the Union columns during the often overlooked Battle of Unison. During the Gettysburg Campaign, a series of cavalry clashes between J.E.B. Stuart and Alfred Pleasonton occurred in the valley at Aldie, Middleburg, Goose Creek, and Upperville. Stuart successfully kept the Federal forces from entering the adjacent Shenandoah Valley and discovering Robert E. Lee's main army. In 1864, as General Jubal Early withdrew from Washington, Union forces attacked his supply wagons at Heaton's Crossroads at present-day Purcellville. In the early winter of 1864, General Phillip Sheridan had the Loudoun Valley put to the torch during The Burning Raid in response to actions of Confederate partisans John Mosby who used the Loudoun Valley as his base of operations. Modern era Following the war, the Loudoun Valley was slow to recover from the devastation of the Burning Raid, but soon the region became a major source of agricultural products again, particularly notable for its numerous dairy farms. Farming remained a main occupation for several generations until the early 1990s when urban growth began encroaching from the east. Though farming has lost its prominence in the valley it maintains a strong presence. Loudoun County ranks 20th in overall agriculture production in the state. Corn, wheat and beans remain staple