The Northeast became a leader in commerce because of its location and early development of industrial industries. The Northeast became a manufacturing hub in the colonies and in the newly formed United States which created specialization and the growth of commerce in this region relative to the South which was more agriculturally based.
The answer is A. Appalachian Mountains
When American colonists headed west they crossed what will known today as the Appalachian Mountains.
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This is true northern Asia has a cold desert climate