American Civil War: The Army of Northern Virginia crosses the Potomac River at White's Ford in the Maryland Campaign.

The American Civil War was a civil war in the United States between the Union and the Confederacy, which was formed in 1861 by states that had seceded from the Union. The central conflict leading to war was a dispute over whether slavery should be permitted to expand into the western territories, leading to more slave states, or be prohibited from doing so, which many believed would place slavery on a course of ultimate extinction.

The Army of Northern Virginia was a field army of the Confederate States Army in the Eastern Theater of the American Civil War. It was also the primary command structure of the Department of Northern Virginia. It was most often arrayed against the Union's Army of the Potomac.

The Potomac River is in the Mid-Atlantic region of the United States and flows from the Potomac Highlands in West Virginia to Chesapeake Bay in Maryland. It is 405 miles (652 km) long, with a drainage area of 14,700 square miles (38,000 km²), and is the fourth-largest river along the East Coast of the United States. More than 6 million people live within its watershed.

White's Ford was an important ford over the Potomac River during the American Civil War. It was used in many major actions, including the crossing into Maryland of the Confederate army prior to the Maryland Campaign and Confederate Major General J.E.B. Stuart's ride around Union Major General George B. McClellan on October 10, 1862, when he used the ford to cross into Loudoun County, Virginia. It is located a few miles above present-day White's Ferry.