Maj. Gen. Fitz John Porter, USA
Brig. Gen. William Pendleton and Maj. Gen. A.P. Hill, CSA
Though both sides had larger forces nearby, brigade-sized forces engaged.
There were just over 600 casualties in total.
A day after the tactical draw at Antietam, Lee began to withdraw back across the Potomac at Shepherdstown. He sent 44 guns of the reserve artillery, under his chief of artillery General William Pendleton, ahead and posted them on the bluffs over the river. Most of the Army of Northern Virginia was back in northern Virginia by dawn, after an all-night crossing. Pendleton with two small brigades of infantry (after the grueling campaign weaker than one normal regiment) was the rearguard to prevent rapid Union pursuit.
Potomac River Ford Known as Boteler's Ford, Blackford's Ford, Pack Horse Ford, and other names, the shallow crossing of the Potomac River less than a mile downstream from Shepherdstown, West Virginia, was used by travelers since prehistoric times. After the highway bridge at Shepherdstown was destroyed early in the Civil War, the ford was a convenient crossing point between Confederate Virginia (this area would become West Virginia after June 20, 1863) and the border state of Maryland. It would become the center of the Battle of Shepherdstown when McClellan finally tried to pursue Lee, and the abandoned cement plant at the bottom of the Virginia bluffs would see bloody battle.
From the James E. Taylor Sketchbook, 1864, looking from Shepherdstown southeast toward the ford.
Union cavalry arrived on the Maryland side of the river soon after dawn on the 18th and began to probe the Confederate position across the Potomac with artillery and rifle fire. Under orders from McClellan to pursue the enemy, Fitz John Porter's 5th Corps took over from the cavalry about two hours later. Porter aggressively deployed more cannon and ordered the First U.S. Sharpshooters and a company of the 5th New York forward. They used the dry trench of the C & O Canal as cover and began to snipe Confederate gunners on the far bank. Some Union artillery shells hit Shepherdstown itself, causing confusion and chaos among the townspeople and wounded rebels left there.
Union artillery fires across the Potomac River. Drawing from Frank Leslies' Illustrated Newspaper, October 25, 1862.
As the day wore on, the Union fire steadily increased and at the same time the Confederate guns began to run low on ammunition; Pendleton spread his infantry to cover the guns. He decided one day’s delay was all he could win, and gave orders for the cannon to withdraw under cover of darkness, reporting that "it was, of course, a critical and anxious hour."
Pendleton's anxiety increased as Union infantry finally crossed the river. Just before dark about 500 men waded across under the cover of protective fire over their heads (this was easier since the Confederates were on a bluff) and forced the Confederate infantry back. The Southerners managed to pull most of their cannon out, but the raiding party was able to capture five pieces. The Yankees pulled back to the east side of the river for the night, taking their captured guns with them. In the confusion and darkness, however, Pendleton came close to panic and reported to Lee that Union forces had captured the entire reserve artillery. Lee and Jackson knew the value of his main artillery: without artillery he would be severely hampered either attacking or defending. He ordered A. P. Hill's and Jubal Early's divisions to turn around and drive the pursuers back into Maryland.
As the Confederates reacted to the assumed crisis, Union commanders were planning a follow-up to their raid. Three brigades of 5th Corps crossed the Potomac at 7:00am on September 19 and headed toward Shepherdstown on the Charlestown Road. Advanced skirmishers soon met A. P. Hill's division as it advanced from the west. Porter reacted quickly to the reports. The Confederates were advancing in force, and he had only a small force on the Virginia side, so he gave orders for all Union troops to return to Maryland.
The 118th Pennsylvania enters the Potomac from Maryland. Harpers Weekly, October 11, 1862.
Now the Union artillery covered a retreat, and most Yankees began to wade back across. But Colonel Charles M. Prevost, commanding the newly formed 118th Pennsylvania Infantry (known as the Corn Exchange Regiment), refused to withdraw until he received orders through the chain of command from his direct superior. Hill's Confederates smashed into the Pennsylvanians just as they were deploying atop the bluffs overlooking the ford.
Their first battle was the first chance many of the Pennsylvanians had to discover their Enfield rifles were defective and would not fire. Prevost was wounded trying to steady his men, then other officers led a bayonet charge which promptly failed. With the commander down, defective weapons, and no prospect of success, the regiment broke apart. Some tried to escape by climbing down the bluffs under Confederate fire, and many died as they fell to the rocks below. Others picked their way past the old cement mill, ran across the slippery dam, or waded the ford. Of the 700 men in the 118th who crossed the river that morning, only 431 came back.
The Confederate victory had more than tactical results. The size of the force Lee used (based on mistaken information) convinced McClellan that the Southern army was still full of fight. His natural caution kicked in, and he decided to delay any further effort to pursue until reinforced. The Battle of Shepherdstown ended the Maryland Campaign, Lee's first invasion of the North.