The United States began pushing westward from the moment it gained independence from Britain in 1783. Foreign powers were involved in North America during this period, too, before American hegemony became firmly established. The American push westward was known as Manifest Destiny.
The earliest area of contention was the Northwest Territory. Although this region had been ceded to the US in 1783, the British continued to maintain a presence there. They also sometimes encouraged Indians in the region to resist the United States. The US finally solidified its grasp on the region by the end of the War of 1812.
In 1803, the US was fortunate enough to have the opportunity to buy the Louisiana Purchase from France. Napoleon needed the money, and he knew he could not defend it against the British. Therefore, it was a bargain for America, and the country doubled in size.
The most egregious American involvement in the affairs of a foreign power concerned Mexico. Mexico controlled Texas until 1936;...
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