The 'Alaska Purchase' was the United States' acquisition of the Alaska territories from the Russian Empire on March 30, 1867, by a treaty ratified by the United States Senate, and signed by president Andrew Johnson.

Russia decided to sell its Alaska territory, fearing that it might be seized if war broke out with the United Kingdom. Russia's primary activities in the territory had been fur trade and missionary work among the Native Alaskans. The land added 586,412 square miles (1,518,800 sq km) to the territory of the United States.