Final answer:
The Louisiana Purchase, completed in 1803, is indeed the historical event that nearly doubled the size of the United States, making the statement true.
Step-by-step explanation:
The statement related to the Louisiana Purchase mentions it doubled the territory of the United States. This is true. The Louisiana Purchase was a significant event in American history that occurred in 1803 when the United States purchased approximately 828,000 square miles of territory from France at a cost of about $15 million. This land deal nearly doubled the size of the United States, extending the nation's boundary to the Rocky Mountains and more than doubling its territory, fostering westward expansion.