Final answer:
The largest land purchase made by the United States was The Louisiana Purchase in 1803, which doubled the size of the country.
Step-by-step explanation:
The largest land purchase made by the United States was The Louisiana Purchase. It occurred in 1803 and involved the acquisition of approximately 828,000 square miles of land from France, doubling the size of the United States. This purchase included parts of present-day states such as Louisiana, Arkansas, Missouri, Iowa, Oklahoma, Kansas, Nebraska, and parts of Minnesota, North Dakota, South Dakota, New Mexico, Texas, Montana, Wyoming, and Colorado.
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