Answer:
The Louisiana Purchase of 1803 brought into the United States about 828,000 square miles of territory from France, thereby doubling the size of the young republic. What was known at the time as the Louisiana Territory stretched from the Mississippi River in the east to the Rocky Mountains in the west and from the Gulf of Mexico in the south to the Canadian border in the north. Part or all of 15 states were eventually created from the land deal, which is considered one of the most important achievements of Thomas Jefferson’s presidency.
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In a speech to Congress in 1823, President James Monroe warned European powers not to attempt further colonization or otherwise interfere in the Western Hemisphere, stating that the United States would view any such interference as a potentially hostile act. Later known as the Monroe Doctrine, this policy principle would become a cornerstone of U.S. diplomacy for generations.
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The Homestead Act was enacted by the U.S. government to settle the open West (for the North, because this went down during the Civil War). It also had the side benefit of reducing population in over-crowded eastern cities by enticing people to hit the trails and head out west.
