In 1917, Washington paid $25 million in gold for three Caribbean islands in a transaction forced by World War I. The agreement included a secret pact that recognized Danish sovereignty over Greenland.
While President Donald Trump revives the controversy over Greenland, history reminds us that the United States already managed to buy Danish territory once: the Virgin Islands, acquired in 1917 in a transaction marked by the pressure of World War I.
The purchase of the then-called “Danish West Indies”—the islands of Saint Thomas, Saint John, and Saint Croix—was finalized on March 31, 1917, for $25 million in gold, equivalent to approximately $500-600 million today.
The agreement, however, was the result of half a century of failed negotiations that were only unlocked under wartime pressure, as recalled in a note published by RFI.
The urgency of war
With the opening of the Panama Canal in 1914, Washington was determined to secure Caribbean shipping routes. The fear was that Germany could seize the Danish islands, located just east of Puerto Rico, and use them as naval bases to threaten American shipping and hemispheric security.
For Denmark, the colonies had ceased to be profitable decades earlier. The abolition of slavery in 1848 had undermined the sugar economy, and the islands had become a financial and administrative burden.
Previous attempts at a sale had failed: first blocked by the U.S. Senate in 1867, then by the Danish parliament in 1902, despite strong local support for the American government.
Diplomatic pressure
In 1916, the balance of power shifted. With the war consuming Europe, American diplomats made it clear that not acquiring the Danish islands carried risks.
Secretary of State Robert Lansing warned that Washington might occupy the islands to prevent their use by Germany if Denmark did not agree to sell. Neutral and vulnerable, Copenhagen yielded.
The treaty was signed on August 4, 1916. The U.S. Senate ratified it that same year, and the formal transfer of sovereignty took place on March 31, 1917, a date still celebrated in the Virgin Islands as “Transfer Day.”
A parallel agreement on Greenland
But there was a parallel diplomatic agreement: the United States formally recognized “Denmark’s right to extend its political and economic interests over the whole of Greenland.”
This declaration, signed by Lansing, was part of the Convention between the United States and Denmark for the cession of the Danish West Indies and helped secure Denmark's sovereignty over the Arctic island for more than a century.
Later attempts
However, with the onset of the Cold War, Washington continued its attempts to acquire Greenland.
In 1946, President Harry Truman's administration made a secret offer to buy Greenland from Denmark for $100 million in gold, plus rights to an oil field in Alaska. Secretary of State James Byrnes presented the offer to Danish Foreign Minister Gustav Rasmussen on December 14, 1946.
Truman's advisors viewed Greenland as an essential strategic defense position against Soviet bombers that might fly over the Arctic Circle toward North America.
The Danish minister was shocked by the proposal and rejected it, but the United States eventually gained access to Greenland through Denmark's membership in NATO in 1949 and a bilateral defense agreement that explicitly stipulated “full respect for the sovereignty of each Party.”
The 1946 offer was revealed in 1991 when declassified documents were discovered.
In 1955, the Joint Chiefs of Staff proposed to President Eisenhower that the nation try again to buy Greenland, but the State Department responded that the time for such a plan had passed. According to diplomatic documents preserved in the U.S. National Archives, discussions about acquiring Greenland have taken place on multiple occasions: in 1867, 1910, 1946, 1955, 2019 during Trump's first term, and now in 2025.
However, the political context has fundamentally changed since 1917. Denmark is no longer a vulnerable neutral state but a member of NATO integrated into European security structures. And Greenland itself enjoys extensive self-government, with a growing national identity.
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