Final answer:
The Appalachian Mountains cross the eastern part of the United States and separate the Atlantic coastal plain from the interior lowlands.
Step-by-step explanation:
The Appalachian Mountains
The mountain range that crosses the eastern part of the United States is the Appalachian Mountains. They stretch from Newfoundland, Canada, to Alabama, USA, and are the oldest mountain range in North America. The Appalachians separate the Atlantic coastal plain from the interior lowlands.
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