Answer: A.Alaska
The United States acquired Alaska from the Russian Empire on March 30, 1867. This was done by a treaty ratified by the Senate of the United States and signed and approved by the then President of USA,Andrew Johnson.
Russia sold Alaska for a price of $7.2 million. This was done as the living conditions were difficult and due to the lack of natural resources. In 1896 gold was discovered in Alaska. Alaska added an area of 586,412 square miles (1,518,800 km2) to the United States of America.