Alaska Purchase
U.S. Secretary of State William Seward wrote to Russian minister Eduard de Stoeckl proposing the purchase of Alaska (March 23, 1867). The following week Stoeckl wrote a response that the Tsar agreed to the American terms.
Treaty concerning the Cession of the Russian Possessions in North America by his Majesty the Emperor of all the Russias to the United States of America : (June 20, 1867).