The dynamic celestial Native American calendar of Devil’s Den Gettysburg, Pennsylvania, USA

Gettysburg’s legacy is a well-chronicled highlight of American history. However, its significance as a revered battleground overshadows a forgotten Iroquoian group (Susquehannock) that occupied the region. The battlefield contains a diabase outcrop known as Devil’s Den that displays rounded blocks and weathered rectangular joints. Field reconnaissance identified a leaning rock slab that forms openings aligned to the summer and winter solstices. Moreover, the rock openings align with the rising and setting of Pleiades and Sirius, respectively, stellar objects tracked by northeastern Native Americans for agricultural and religious purposes. A petroglyph-bearing rock shadowed by the slab is the first known occurrence of petroglyphs in Adams County and only the 22nd documented case in Pennsylvania. Petroglyphs relating to select cardinal directions, Ursa major, and Manitou (Great Spirit manifestations) were situated for sunlight to interact with them during certain times of the year. The discovery of an Iroquoian calendar implies the region was utilised by a sedentary society.