Why did the Americans want to expand across the continent?

"The primary reason the U.S. expanded its influence in foreign countries: Economic reasons – industrialization in the late 1800s increased the need to trade with other countries. Sales of American goods to foreign countries were important to the workers in the U.S."

Explanation: "One of the main reasons was for personal economic gain. Many Americans believed that if they could not succeed where they were, they could always move West and start over. After all, that was how the nation had grown so large. The Panic of 1837 was an incentive for many, but the migration had begun before then."

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