Final answer:
The Eastern Lowlands are a flat coastal plain that runs along the Atlantic Ocean and the Gulf of Mexico.
Step-by-step explanation:
The flat coastal plain that runs along the Atlantic Ocean and the Gulf of Mexico is called the Eastern Lowlands. This landform is found in the eastern portion of the United States and extends from New York to Texas. It is a relatively flat zone composed of sediment that has accumulated since the rifting of Pangaea.