The Potomac River was more than the political boundary between the Union and Confederacy in the Civil War. It was a significant physical barrier with limited places where armies could safely cross.

Map of battles along the Potomac River in the American Civil War

Falling Waters (July 1861 – under construction)
Ball’s Bluff (October 1861 – under construction)
Williamsport (June 1861, September 1862, July 1863)
South Mountain (September 1862)
Harpers Ferry (September 1862, July 1863, Fall 1864)
Antietam (September 1862)
Shepherdstown (September 1862)
Monocacy (July 1864)