Special Order 191 Special Order 191 ( the " Lost Dispatch , " and the " Lost Order " ) was a general movement order issued by Confederate Army General Robert E . Lee in the Maryland Campaign of the American Civil War . A lost copy of this order was recovered in Frederick County , Maryland , by Union Army troops , and the subsequent military intelligence gained by the Union played an important role in the Battle of South Mountain and Battle of Antietam . History . The order was drafted on or about September 9 , 1862 , during the Maryland Campaign . It gave details of the movements of the Army of Northern Virginia during the early days of its invasion of Maryland . Lee divided his army into pieces , which he planned to regroup later : according to the precise text Maj . Gen . Stonewall Jackson was to move his command to Martinsburg while McLaws ' s command and Walker ' s command " endeavored to capture Harpers Ferry . " Maj . Gen . James Longstreet was to move his command northward to Boonsborough . D . H . Hill ' s division was to act as rear guard on the march from Frederick . Lee delineated the routes and roads to be taken and the timing for the investment of Harpers Ferry . Adjutant Robert H . Chilton penned copies of the letter and endorsed them in Lee ' s name . Staff officers distributed the copies to various Confederate generals . Jackson in turn copied the document for one of his subordinates , Maj . Gen . D . H . Hill , who was to exercise independent command as the rear guard . Hill said the only copy he received was the one from Jackson . About noon on September 13 , Corporal Barton W . Mitchell of the 27th Indiana Volunteers , part of the Union XII Corps , discovered an envelope with three cigars wrapped in a piece of paper lying in the grass at a campground that Hill had just vacated . Mitchell realized the significance of the document and turned it in to Sergeant John M . Bloss . They went to Captain Peter Kopp , who sent it to regimental commander Colonel Silas Colgrove , who carried it to the corps headquarters . There , an aide to Brig . Gen . Alpheus S . Williams recognized the signature of R . H . Chilton , the assistant adjutant general who had signed the order . Williams forwarded the dispatch to Maj . Gen . George B . McClellan , the commander of the Army of the Potomac . McClellan was overcome with glee at learning planned Confederate troop movements and reportedly exclaimed , " Now I know what to do ! " He confided to a subordinate , " Here is a paper with which , if I cannot whip Bobby Lee , I will be willing to go home . " McClellan stopped Lee ' s invasion at the subsequent Battle of Antietam , but many military historians believe he failed to fully exploit the strategic advantage of the intelligence because he was concerned about a possible trap ( posited by Maj . Gen . Henry W . Halleck ) or gross overestimation of the strength of Lee ' s army . The hill on the Best farm where the lost order was discovered is located outside of Frederick , Maryland , and was a key Confederate artillery position in the 1864 Battle of Monocacy . A historical marker on the Monocacy National Battlefield commemorates the finding of Special Order 191 during the Maryland Campaign . Corporal Mitchell , who found the orders , was subsequently wounded in the leg at Antietam and was discharged in 1864 due to the resulting chronic infection . He died in 1868 at the age of 52 . His wife received a pension in 1890 . In popular culture . In Harry Turtledove ' s Southern Victory Series alternate history novels , the point of divergence with recorded history is that the order is not discovered by Union troops , but is instead recovered by a trailing Confederate soldier . Without it , McClellan is unable to find Lee ' s army and the Battle of Antietam is not fought . Lee reaches Philadelphia and forces McClellan to fight in an unfavorable position . The Confederate States of America is able to crush the Army of the Potomac at Camp Hill , securing with the win support from Britain and France , so the Emancipation Proclamation never occurs , and the Union is forced to give the Confederate states independence . The USA and CSA with their allies ( the USA eventually allies with the World War I - era Central Powers ) go on to fight three more bloody wars , first being the fictional Second Mexican War and the last two wars being alternate versions of World War I and World War II . Union troops not discovering the order is also the point of divergence for the alternate reality superhero comic book series Captain Confederacy . In the game Chrononauts , this event is on the timeline . Bernard Cornwell ' s novel " The Bloody Ground " , part of the Starbuck Chronicles , fictionalises the events and lead - up of Antietam , in which the order is central to the drama in the lead - up to the battle and an explanation is offered for how it ended up discarded in the field .