Which purchase in 1867 involved the acquisition of 365 million acres?

The acquisition of 365 million acres refers to the Alaska Purchase, which was negotiated and finalized in 1867 when the United States purchased Alaska from Russia. This transaction marked a significant expansion of U.S. territory, as Alaska is the largest state in the country by area. The purchase was originally met with some skepticism, being referred to as "Seward's Folly" after Secretary of State William H. Seward, who facilitated the deal. However, it later proved to be a valuable acquisition with vast natural resources, including gold, oil, and fish. This historical context clarifies the significance of the Alaska Purchase compared to the other options listed, which involve smaller areas and different historical contexts.