The significance of the purchase of Alaska in American history lies in its strategic, economic, and symbolic implications. Acquired from Russia in 1867 for $7.2 million, the purchase was initially criticized by some as "Seward's Folly," referring to Secretary of State William H. Seward's efforts in the acquisition. However, Alaska proved to be rich in natural resources, including gold, oil, and minerals, contributing to economic growth and expansion. Additionally, the acquisition completed the continental United States, enhancing American sovereignty and territorial integrity. The purchase symbolized the nation's commitment to expansion and the idea of Manifest Destiny in the 19th century.