Final answer:
The Appalachian Mountains presented the greatest barrier to westward migration.
Step-by-step explanation:
The geographic feature that presented the greatest barrier to the westward migration of American settlers during the colonial period was the Appalachian Mountains.
These mountains, located in the eastern part of North America, stretch from the Canadian provinces of Quebec and Newfoundland and Labrador to central Alabama in the southeastern United States. They formed a significant obstacle for early settlers due to their size, rugged terrain, and dense forests.
The Appalachian Mountains acted as a natural barrier that limited westward expansion, forcing settlers to find alternative routes such as the Cumberland Gap and the Wilderness Road to access the western frontier.
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