United States takes possession of Alaska after purchasing it from Russia for $7.2 million. Celebrated annually in the state as Alaska Day.

The Alaska Purchase was the purchase of Alaska from the Russian Empire by the United States for a sum of $7.2 million in 1867. On May 15 of that year, the United States Senate ratified a bilateral treaty that had been signed on March 30, and American sovereignty became legally effective across the territory on October 18.

The Russian Empire was an empire that spanned most of northern Eurasia from its establishment in November 1721 until the proclamation of the Russian Republic in September 1917. At its height in the late 19th century, it covered about 22,800,000 km² (8,800,000 sq mi), roughly one-sixth of the world's landmass, making it the third-largest empire in history, behind only the British and Mongol empires. It also colonized Alaska between 1799 and 1867. The empire's 1897 census, the only one it conducted, found a population of 125.6 million with considerable ethnic, linguistic, religious, and socioeconomic diversity.

Alaska Day is a legal holiday in the U.S. state of Alaska, observed on October 18. It is the anniversary of the formal transfer of territories in present-day Alaska from the Russian Empire to the United States, which occurred on Friday, October 18, 1867.