Final answer:
The largest single land acquisition in U.S. history is the Louisiana Purchase, which occurred in 1803 when the United States doubled its size by purchasing the territory from France for $15 million.
Step-by-step explanation:
The Largest Single Land Acquisition in U.S. History
The largest single land acquisition in U.S. history is the Louisiana Purchase. This transaction took place in 1803 when the United States, under the presidency of Thomas Jefferson, bought the Louisiana Territory from France for $15 million. The deal effectively doubled the size of the United States, adding a vast amount of land that stretched from the Mississippi River to the Rocky Mountains and from the Gulf of Mexico to Canada. This historic purchase provided the United States with control over the strategic Mississippi River and the port of New Orleans, both essential for trade and westward expansion. The Louisiana Purchase is often regarded as one of the greatest real estate deals in history and a significant event that shaped the nation.
Regarding the other options provided in the question, the Mexican Cession occurred after the U.S. victory in the Mexican-American War and the signing of the Treaty of Guadalupe Hidalgo in 1848. Although it represented a significant increase in the U.S. landmass, it was not larger than the Louisiana Purchase. The Gadsden Purchase, made in 1854, involved a smaller acquisition of land from Mexico to facilitate the construction of a southern transcontinental railroad. The Alaska Purchase in 1867, while significant in size, was also not larger than the Louisiana Purchase.
Therefore, the answer to the student's question is: a. Louisiana Purchase.