Jefferson Rock is a rock formation on the Appalachian Trail above lower Harpers Ferry in Harpers Ferry National Historical Park. It consists of several large masses of shale rock, piled one upon the other, that overlook the Shenandoah River just prior to its confluence with the Potomac River. The name of this landmark derives from Thomas Jefferson, who stood there on October 25, 1783. He found the view from the rock impressive and wrote in Notes on the State of Virginia that "this scene is worth a voyage across the Atlantic".
The uppermost slab of Jefferson Rock originally rested on a natural stone foundation so narrow that one was able to sway the rock back and forth with a gentle push. Because this natural foundation had "dwindled to very unsafe dimensions by the action of the weather, and still more, by the devastations of tourists and curiosity-hunters," four stone pillars were placed under each corner of the uppermost slab sometime between 1855 and 1860.