A century ago today, the United States Congress, acting on the request of President Woodrow Wilson, declared war on Imperial Germany. Four days before, on the evening of April 2, the president addressed a joint session of Congress, asking for war. The subsequent vote was hardly close, with the House voting 373 to 50 in favor, while the Senate’s tally of 82 to six was even more lopsided.
This was the most important foreign policy decision made by Washington in the entire 20th century, since by entering the First World War—called the Great War at the time—the United States determined the outcome of that momentous and horrible conflict and thereby set Europe on a course for an even more terrible war to come.
http://observer.com/2017/04/100-year-anniversary-world-war-one/