Gathland State Park is a small park near South Mountain, MD.  It significance is it's connection to the Civil War.  The AT runs through Gathland.  Below is a small excerpt from the Gathland State Park website:

Gathland State Park was once the mountain home of George Alfred Townsend, a Civil War journalist. It is the site of a unique collection of buildings and structures that he designed and constructed, some of which have been restored. A large, stone monument dedicated to war correspondents is an outstanding attraction at this day use park. (140 acres) The Appalachian Trail traverses the park and passes the monument base. Maryland has 37.5 miles of the interstate hiking trail. The park includes all of Crampton's Gap, which was the southern most gap fought over during the battle of South Mountain. Fought September 14, 1862, it was the first major battle of the Civil War fought in Maryland.