Fall Line: Definition & Cities

Instructor: Suzanne Rebert

Suzanne has taught college economics, geography, and statistics, and has master's degrees in agricultural economics and marine affairs (marine resource management).

In the Eastern United States, you can see a dramatic shift from the coastal plain to the inland mountains. Read about this shift and other fall lines, and take a quiz to test your knowledge.

Location, Location, Location

Why is your city or town where it is? Maybe it has a good natural harbor for ships, or it's close to an important mining area. Geology often provides the clues to patterns of human settlement. For a chain of cities in the Eastern United States, the boundary between two kinds of rock set the stage for conditions that would attract settlers and industries.

What is a Fall Line?

A fall line is a rapid change in elevation. It develops because the erosion characteristics of the two kinds of rock that meet at the line are dramatically different. In the Eastern United Stats, the harder bedrock of the hills (the Piedmont) resists erosion, while the softer rock of the coastal plain is easily worn away. Therefore, instead of a smooth, gradual slope from the Appalachian crest to the Atlantic Ocean, there is a plateau with a noticeably steep drop to the coastal plain.

Geologic map showing the fall line of the U.S. Eastern seaboard
fall line of US Eastern seaboard

As a result, rivers along the Eastern seaboard are characterized by waterfalls and rapids. At these places, Native Americans and early European traders and settlers were forced to portage their canoes and other boats, making these natural sites to stop for rest and refreshment.


The Eastern seaboard's fall line was important for the early economic development of the United States, because the dramatic elevation change allowed falling water to serve as a source of energy. Early mills used machinery powered directly by water; later, turbines turned the water's power into electricity. Where mills and other industries grew, people came to work and trade, and many of the largest East Coast cities arose over time. A few examples are given below.

Trenton, New Jersey

Falls of the Delaware at Trenton, New Jersey
Falls of the Delaware at Trenton, NJ

Trenton is the state capital of New Jersey, but at one time it was briefly in the running for capital of the United States. Although Southerners successfully pushed for a site farther south, Trenton has still played an important historic and economic role. Founded by Quaker settlers, it was the site of the Revolutionary War's Battle of Trenton and General Washington's famous crossing of the Delaware River. Mills powered by the river produced pottery and wire rope, attracting many European workers who settled here during the 19th century.

The Great Falls of the Potomac

Great Falls National Park on the Potomac River near Washington, D.C.
Great Falls of the Potomac

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