On March 30 1867, the US bought Alaska from Russia for $7,200,000 (2 cents an acre - "Seward's Folly"). From the article:
"U.S. Purchase of Alaska ridiculed as "Seward's Folly” U.S. Secretary of State William H. Seward signs a treaty with Russia for the purchase of Alaska for $7 million. Despite the bargain price of roughly two cents an acre, the Alaskan purchase was ridiculed in Congress and in the press as “Seward’s Folly,” “Seward’s icebox,” and President Andrew Johnson’s “polar bear garden.”
The czarist government of Russia, which had established a presence in Alaska in the mid-18th century, first approached the United States about selling the territory during the administration of President James Buchanan, but negotiations were stalled by the outbreak of the Civil War. After 1865, Seward, a supporter of territorial expansion, was eager to acquire the tremendous landmass of Alaska, an area roughly one-fifth the size of the rest of the United States. He had some difficulty, however, making the case for the purchase of Alaska before the Senate, which ratified the treaty by a margin of just one vote on April 9, 1867. Six months later, Alaska was formally handed over from Russia to the United States. Despite a slow start in U.S. settlement, the discovery of gold in 1898 brought a rapid influx of people to the territory, and Alaska, rich in natural resources, has contributed to American prosperity ever since."