It's not a mountain range or a specific elevation feature, but rather a geological boundary marked by a series of waterfalls and rapids. This line stretches from Maine down to Alabama, marking the transition zone between the hard, resistant rocks of the Piedmont Plateau and the softer, sedimentary rocks of the Coastal Plain.

The Fall Line was significant historically because it served as a natural barrier to westward expansion and also provided a source of hydropower. Many major cities, like Richmond, Virginia, and Augusta, Georgia, developed along the Fall Line.