On September 13th, at Frederick, Maryland, General George McClellan received some valuable intelligence. This was a copy of General Robert E. Lee’s Special Orders No. 191 written on September 9th, 1862. In it was written orders disclosing the location(s) of Lee’s Confederate army that was divided into several sections. If McClellan could attack these sections before Lee had time to concentrate his army, McClellan might be able to destroy the Army of Northern Virginia in Maryland. While in communications with Washington, McClellan had to verify the authenticity of Lee’s orders, after all four days had gone by since Lee issued them, and many things could have changed.
McClellan heard reports from the civilians of the area stating that a large Confederate force was spotted in and near Hagerstown, as well as Pleasant Valley. A major factor that contributed to McClellan’s hesitation was the fact that as of the 13th, the garrison at Harper’s Ferry still had not surrendered. This could only mean that those portions of Special Orders 191 were not carried out. Despite many rumors circulating as to the whereabouts of the Confederate army, McClellan must learn their true position in order to prepare his Army of the Potomac for an assault.
McClellan sent a copy of the lost Confederate orders to General Alfred Pleasonton, to see if the orders were still being followed by the Confederates. Although Pleasonton had made his way to the foot of South Mountain, as dusk fell upon the Middletown Valley, he was still uncertain if the orders were being followed. Pleasonton did report hearing the sound of gunfire in the direction of Harper’s Ferry. Based on the information from Pleasonton, information from locals, and information coming from Sugarloaf Mountain from the signal corps, McClellan made a decision to advance his Union army.
During the evening, McClellan sent orders to his Corps commanders. General Burnside was ordered to take his wing and seize Turner’s Gap on September 14th. General Reno, who was part of Burnside’s wing, was to take his Ninth Corps and march to Middletown. General Joseph Hooker’s First Corps, still sitting on the banks of the Monocacy River, was to move in support and assist if necessary, in the capture of Turner’s Gap during the day of the 14th. General Edwin Sumner’s two corps was to move behind Hooker and bivouac in Middletown as reserves.
Further to the south, near Buckeystown in Frederick County, was the Sixth Corps led by General William Franklin. McClellan wrote in Franklin’s orders: “I have reliable information that the mountain pass by this road is practicable for artillery and wagons. If this pass is not occupied by the enemy in force, seize it as soon as practicable, and debouch upon Rohrersville, in order to cut off the retreat of or destroy McLaws’ command. If you find this pass held by the enemy in large force, make all your dispositions for the attack, and commence it about half an hour after you hear severe firing at the pass on the Hagerstown pike, where the main body will attack. Having gained the pass, your duty will be first to cut off, destroy, or capture McLaws’ command and relieve Colonel Miles. If you effect this, you will order him to join you at once with all his disposable troops, first destroying the bridges over the Potomac, if not already done, and leaving a sufficient garrison to prevent the enemy from passing the ford, you will then return by Rohrersville on the direct road to Boonsborough if the main column has not succeeded in its attack. If it has succeeded, take the road by Rohrersville to Sharpsburg and Williamsport, in order either to cut off the retreat of Hill and Longstreet toward the Potomac, or prevent the repassage of Jackson. My general idea is to cut the enemy in two and beat him in detail. I believe I have sufficiently explained my intentions. I ask of you, at this important moment, all your intellect and the utmost activity that a general can exercise.”
McClellan had an opportunity to destroy Lee’s army while it remained divided. He would call upon General William Franklin and his Sixth Corps to deliver the first major blow to the Confederate invasion. For McClellan, the key seemed to be on Turner’s Gap and Crampton’s Gap. McClellan wrote on October 15th, 1862: “The carrying of Crampton’s Pass, some 5 or 6 miles below, was also important to furnish the means of reaching the flank of the enemy, and having, as a lateral movement, direct relations to the attack on the principal pass, while it at the same time presented the most direct practicable route for the relief of Harper’s Ferry.”
As September 14th dawned, Franklin’s Corps moved out of Jefferson and arrived in Burkittsville around noon. General Franklin was to be the deciding factor in the beginning phases of splitting Lee’s army in half. Immediately after arriving at Burkittsville problems began for Franklin. He found that the passage of Crampton’s Gap was in possession of Confederate cavalry, infantry and artillery. At 2:00 pm McClellan received a dispatch from Franklin. McClellan wrote back to Franklin telling him to hold Burkittsville at any cost. McClellan also wrote that if he found the passage through South Mountain to be occupied by Confederate soldiers Franklin was to amuse them as reserves may be available to assist Franklin. As the Sixth Corps arrived on the outskirts of Burkittisville, Franklin ordered his men to bivouac and prepare rations. In the meantime Franklin was making his plan of attack and communicating with McClellan, whose headquarters were located near Middletown.
Late in the day, Franklin launched his assault upon Crampton’s Gap and, after a few hours of heavy fighting, he took possession of the Crampton’s Gap. Franklin’s Sixth Corps had smashed through Crampton’s Gap, but upon seeing a portion of McLaws’ and Anderson’s divisions deployed in Pleasant Valley, decided not to press on, fearing the surrender of Harper’s Ferry was imminent. Franklin was ordered to follow the Confederate force as rapidly as possible but night time quickly fell upon the battlefield and that plan was abandoned. Franklin was satisfied with his achievements and seeing a large force in Pleasant Valley, did not follow the retreating army. During the night, the cavalry escaped from Harper’s Ferry and made their way through enemy held territory, which meant that the garrison at Harper’s Ferry still in Union hands.
On the night of the Battle of South Mountain orders were given to the Union corps commanders “to press forward their pickets at early dawn”. General Franklin was ordered to move into Pleasant Valley and “occupy Rohrersville by a detachment, and endeavor to relieve Harper’s Ferry.” At the same time, Generals Burnside and Porter, upon reaching the road from Boonsboro to Rohrersville, were instructed “to reinforce Franklin or to move on Sharpsburg, according to circumstances.”
The next day, Smith’s Division of Franklin’s Corps moved down the valley toward Weverton. Arriving at Garrett’s Mill, and taking the road that led to Sandy Hook, Smith halted his division upon seeing numbers superior to his own and being so far from reinforcements, pulled back. However, the firing at Harper’s Ferry ceased, indicating that a surrender had taken place. Franklin was too late and McLaws’ and Anderson’s thinly stretched divisions were spared. The Battle for Pleasant Valley near Weverton or Sandy Hook was not to be.
The Battle of South Mountain had stalled McClellan’s army. The fighting that took place at Turner’s, Frostown and Fox’s Gaps brought Lee the time he needed in order to carry on with the Maryland Campaign and get his army concentrated Sharpsburg. The Battle of Crampton’s Gap although is part of the Battle of South Mountain is in deed a separate action that could have been disastrous for the Confederate army during the Siege of Harper’s Ferry. If Franklin could have followed up on his victory at Crampton’s Gap, he could have cut McLaws and Anderson off striking a major blow and winning a decisive victory. As a result of the battles at South Mountain and the surrender of Harper’s Ferry, General Lee ordered the concentration of his Confederate army at Sharpsburg. McClellan and Lee would meet on farmland surrounding Sharpsburg, where the Battle of Antietam would begin.