Abraham Lincoln regularly complained that his Union commander George B. McClellan suffered from "the slows." Historians generally agree that McClellan was superb in organizing and training his troops, but most say he seemed reluctant to risk them in battle.
When Confederate Gen. Robert E. Lee invaded the North in September 1862, he had hopes of reaching the Susquehanna River and capturing Harrisburg before McClellan would be ready to oppose him.
The Virginian had taken a chance, dividing his army to capture the federal garrison at Harper's Ferry. To Lee's surprise, the usually cautious McClellan had advanced with uncharacteristic speed.
"Special Orders 191" was part of the reason for the change in McClellan's behavior.
On Sept. 9, Lee was camped outside Frederick, Md., when he instructed a senior aide to write and send instructions to his generals on their movements for the next few days. One copy, addressed to Gen. D.H. Hill, was found Sept. 13 near Lee's former headquarters by soldiers from 27th Indiana Volunteer Infantry. The orders were wrapped around several cigars
By that evening, McClellan, acting on the information in Lee's orders, was moving to confront the Confederates before they could reunite their forces.
The copy of "Special Orders 191" is on display through Oct. 31 at the Monocacy Battlefield visitors center. The center, on state Route 355 south of Frederick, is less than a mile from where Lee had been camped.
The document's usual home is the Library of Congress, and the sesquicentennial of the Battle of Antietam marks the first time the one-page order -- written in pencil on blue-lined paper -- has been brought back to where it was created.
The visitors center also houses a long-term exhibit dealing with the July 9, 1864, battle of Monocacy Junction during the third Confederate invasion of the North. Although the mostly inexperienced Union troops were forced to withdraw, they temporarily halted a rebel army under Gen. Jubal Early headed for Washington, D.C. That delay offered additional time to send Union reinforcements to strengthen defenses around the federal capital.
Historians continue to disagree on how well McClellan used the lost orders in 1862.
He spent several days arranging his troops before attacking the Confederates at Antietam, and the resulting battle was a near-draw. When Lee began his withdrawal back into Virginia, McClellan failed to stop him from crossing the Potomac River, and the bloody conflict continued for another 21/2 years.