Final answer:
Gaining control over the Mississippi River led to conflicts with American Indians and the need for the U.S. military to spread over a wider area.
Step-by-step explanation:
The subject of this question is History. The question is asking about the consequences of gaining control over the Mississippi River and the impact on the territories becoming new states.
One of the consequences of gaining control over the Mississippi River was that the U.S. military was forced to spread over a wider area. This was necessary to protect and maintain control over the newly acquired territories and states.
Additionally, gaining control over the Mississippi River led to conflicts arising between settlers and American Indians. As American settlers moved into the new territories, they came into conflict with Native American tribes who already inhabited the region.
It is important to note that gaining control over the Mississippi River did not directly result in manufacturing becoming the largest sector of the U.S. economy nor did it cause populations in eastern states to rapidly decline. Therefore, options A and B are not accurate.
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