Special Order 191

Special Order 191 (series 1862), also known as the "Lost Dispatch" and the "Lost Order", was a general movement order issued by Confederate Army General Robert E. Lee on about September 9, 1862, during the Maryland Campaign of the American Civil War. A lost copy of this order was recovered on September 13 by Union Army troops in Frederick County, Maryland, and the subsequent military intelligence gained by the Union played an important role in the Battle of South Mountain and Battle of Antietam.