 
<translate> Akụkụ dị mkpa iji zaa ajụjụ a bụ: United States zụtara àgwàetiti ndị ahụ n'aka ndị Denmark na 1917 n'okpuru Nkwekọrịta nke Danish West Indies. Ya mere, azịza ya bụ 1917. <eng> The important part for answering this question is: The islands were purchased from the Danish by the United States in 1917 under the Treaty of the Danish West Indies. So, the answer is 1917. 