"The 31st of March is recognized every year as "Transfer Day" in the United States Virgin Islands. This day commemorates an event that occurred over eight decades ago, when the Danish West Indies were formally ceded to the United States by Denmark; thus, becoming the U.S. Virgin Islands, in exchange for twenty-five million dollars. The United States' interest in the Virgin Islands was primarily for their strategic location, while any economic benefits were secondary. The islands represented a much needed foothold in the Caribbean for the American navy, and later were looked toward as a base to guard the Panama Canal. American negotiations with the Danish government can be characterized as ones of strategic diplomacy. All offers of proposed purchase came on the heels of American military conflicts.
American interest in the Virgin Islands dates back to as early as the mid-1860's. At the eve of the Civil War, budding American imperialism, and the need for a Carribean naval base, prompted Secretary of State William H. Seward to begin to investigate the islands as a possible coaling station for U.S. naval and merchant vessels. On October 24, 1867, after nearly two years of extensive negotiation and a visit to the islands by Seward, himself, the Danish government ratified a treaty, in which Denmark would cede the islands of St. Thomas and St. John to the United States. The price was to be seven and a half million dollars in gold, provided the treaty received the consent of the islands’ population. Unfortunately, within a year the islands were visited by a hurricane, an earthquake, a tsunami and a fire."....read more here http://www.dkconsulateusvi.com/TRANSFER/transfer.html.