How much did the United States pay to Russia for Alaska?

7.2 million dollars negotiated in March, 1867 by William Seward, U.S. Secretary of State amd Eduard de Stoeckel of Russia.

Source : Alaska: A History of the 49th State, 2nd ed., ed. by Claus-M. Naske and Herman E. Slotnick. Norman, University of Oklahoma Press, 1987.