Antietam Creek () is a tributary of the Potomac River located in south central Pennsylvania and western Maryland in the United States, a region known as the Hagerstown Valley. The creek became famous as a focal point of the Battle of Antietam during the American Civil War.
Geography
The creek is formed in Franklin County, Pennsylvania, at the confluence of the West and East Branches of Antietam Creek, about south of Waynesboro, Pennsylvania. Welty's Mill Bridge crosses the East Branch of Little Antietam at Washington Township in Franklin County, Pennsylvania. The stream runs for about upon its entering Washington County, Maryland. The course proceeds southward in a meandering pattern, and the creek empties into the Potomac south of Sharpsburg about upstream of Washington.
The watershed area is and includes parts of Franklin County (106 mi<sup>2</sup>) and Washington County (185 mi<sup>2</sup>). Major tributaries in Pennsylvania include the East and West Branches, Red Run and Falls Creek. Major tributaries in Maryland include Little Antietam Creek, Beaver Creek, and Marsh Run. Communities in the watershed include Waynesboro in Pennsylvania; and Boonsboro, Funkstown, Hagerstown, Mount Aetna, Sharpsburg and Smithsburg in Maryland.
At least four different tributaries are named Little Antietam Creek. Little Antietam Creek which empties into the Antietam in Keedysville, Maryland and another below Leitersburg, Maryland. The name Little Antietam Creek is also applied to the East and West Branch in Pennsylvania, the West Branch historically Little Antietam Creek proper. Historical and variant names include Andiedom, Andirton Creek, Ant-eat-em Creek, Anticturn Creek, Antieatum Creek, Crooked Brook, Odieta Creek and Ondieta Creek.