September 19, 1862 found General Robert E. Lee and his Army of Northern Virginia bumping along the roads just south of the Potomac River. The army was battered indeed, but far from broken. The Battle of Sharpsburg had taken its toll on both armies. If Major General George B. McClellan allowed Lee some time, his army would recuperate to become as dangerous as ever. The Federal commander obliged.
McClellan sent an anemic pursuit in the form of a small detachment of cavalry and the Federal V corps of Fitz John Porter. This force was met by artillery and a small force of infantry under William Pendleton at Boteler's Ford near Shepherdstown. Pendleton was in command of the ANV's artillery reserve and had not advanced with Lee into Maryland. He was ordered to guard the fords of the Potomac from Williamsburg to Shephardstown. His force was arrayed on bluffs just south of the ford, forty-four guns and 600 infantry of Armistead's and Lawton's brigades.
At about 8AM the Yankee cavalry appeared on the north bank of the river, a brigade from Pleasonton's command accompanied by five batteries of horse artillery. The Federal gunners began shelling the Confederate position and soon drove the Rebel gunners away from many of their pieces. A little later the cavalry was joined by the men of Porter's Corps and they added a hot musketry to the cannon. The contest lasted throughout the day with Federal and Confederate cannon sparring across the river and sharpshooters of both sides doing their deadly work.  Pendleton and his small force held the Yankees at bay but things were beginning to get complicated. Numerous battery’s had reported to Pendleton that they were nearing the end of their ammunition in the late afternoon and the infantry was being spread thin to cover other possible crossing points along the river. Pendleton had been given discretionary orders by Lee to hold out as long as possible and to retire if the enemy crossed in such strength that would endanger his command. Near dusk he ordered a withdrawal from the area to commence after dark to shield the move from enemy eyes.  Once the movement was underway, the Confederate pickets were driven away from the ford by a strong force of infantry. Pendleton was unable to ascertain the strength of the enemy force and growing anxious he set out to find General Lee. As it developed the gunners of a Confederate battery near the ford had been driven away by musketry and artillery fire and the men that drove in the pickets and caused Pendleton's anxiety were the 4th Michigan Infantry and 1st US Sharpshooters, ordered by Porter to cross the stream and capture those four guns and established a bridgehead. They were withdrawn a couple of hours after dark but it was certainly a disconcerting bit of timing.
At about midnight, Pendleton was announced to General Lee who was camped near Shephardstown. Pendleton told Lee that his infantry had been driven and that all of the guns of the artillery reserve had been captured by an enemy force of unknown strength.
“All?” Lee asked with dismay.
“Yes, General. I fear all.” replied Pendleton.
Unwilling to mount a rash counter attack in the darkness, Lee decided to wait until morning to respond to the threat. He ordered General Thomas J. Jackson to have his nearest division (A.P. Hill) prepared to move toward the ford at the earliest time possible the next morning. 
Early the next morning, General Porter began pushing the divisions of Sykes and Morell with a brigade of cavalry across the Potomac, but before they could get all across they were met by A.P. Hill's men and rousted back to the north bank. That is where they would stay. Much to the relief of Lee, the Federals had not captured any of the reserve artillery nor were they able to take away the four guns they had captured on the 19th.
The Battle at Shephardstown would bring the Confederate campaign in Maryland to a close, but Lee, ever planning, had his mind set for further offensive moves north.
- From Manassass to Appomattox, James Longstreet, page 263
- Memoirs of a Confederate: A Critical Narrative, E. P. Alexander, page 271
- O.R. vol. 19, part 1, p345, pp.831- 834
- R.E. Lee, Douglass S. Freeman, volume 2, p. 407