Why did the United States get involved in the predominantly European conflict, World War I (1914-1918)? Ever since George Washington issued a proclamation of neutrality in 1793, the United States had mostly avoided European conflicts. In the late nineteenth century, however, isolation was not longer possible—due to American imperialism, industrial trade interests, and massive European immigration. On June 28th, 1914, Archduke Franz Ferdinand of the Austro-Hungarian Empire was assassinated in the city of Sarajevo. For a multitude of reasons, this dragged the major European powers and their colonial possessions into a global conflict. US opinion on the war was divided and President Woodrow Wilson at first declared the US neutral. Submarine warfare from German forces, including the sinking of the Lusitania, increased popular and political support for US entry into the war. On April 6, 1917, at the urging of President Woodrow Wilson, the United States Congress declared war. The sources below explore the United States’ brief but eventful involvement in World War I.