31 March - The US bought the Virgin Islands for $25 million

 

The United States purchased the Virgin Islands from Denmark, on 31 March 1917. The U.S. government acquired the Danish West Indies, which included the islands of St. Thomas, St. John, and St. Croix, for the sum of $25 million in gold. This agreement, known as the Treaty of the Danish West Indies, was signed on 04 August 1916, and ratified on 17 January 1917. The official transfer of the islands to the United States took place on 31 March 1917, and they were renamed the United States Virgin Islands.