Here's why:

* The Fall Line is a geological boundary that marks the point where the higher, harder rocks of the Piedmont plateau meet the softer, lower rocks of the Atlantic Coastal Plain.

* The Piedmont Region is the upland area between the Fall Line and the Appalachian Mountains.

So, if you were to travel from west to east, you would first encounter the Appalachian Mountains, then the Piedmont Region, and finally cross the Fall Line into the Coastal Plain.