From east Texas to New Jersey, the boundary between the Gulf/Atlantic Coastal Plain and upland regions (e.g. Georgia's Piedmont) is a wave-cut scarp about 100 million years old, marking a high stand of mid-Cretaceous seas. Where rivers cross this step in the terrain, waterfalls and rapids impede navigation. Numerous cities (e.g. Columbus, Macon, Augusta, Columbia, Raleigh, Richmond, Washington) grew close to the Fall Line where goods and people moving upriver transferred from riverboats to wagons for travel further inland.
Inland of the Fall Line, Georgia's Piedmont has old metamorphic rock, clay-rich soils, and hilly terrain rising to the Blue Ridge mountains. Seaward (southeast) of the Fall Line, the Coastal Plain has young sedimentary rock, sandy soils, and flatter topography reaching to the Atlantic coast and Florida.