August 19 – President Woodrow Wilson announced that the U.S. would remain neutral after the outbreak of war in Europe.
April 19 – President Wilson publically warned Germany not to continue unrestricted submarine warfare policies.
January 19 – Germany’s Foreign Secretary Zimmerman sent a telegram to Mexico urging her to enter the war against the U.S. Mexico refused.
April 6 – After landslide votes in both houses, Congress declared war on Germany.
May 18 – The U.S. passed the Selective Service Act, empowering the federal government to draft men for the armed forces.
July 3 – The first wave of the American Expeditionary Force landed in France.
October 23 – American troops in France fired their first shot in trench warfare.
January 8 – President Wilson declared his Fourteen Points for peace.
March 21 – Germany launched its Spring Offensive and the German advance became difficult for the Allies to halt.
May 31 – American forces stopped Germans on the banks of the Marne near Paris.
November 11 – Fighting ended on the 11th hour of the 11th day of the 11th month.
June 28 – The Treaty of Versailles officially ended the war.
March 19 – The U.S. Senate failed to ratify both the Treaty of Versailles and U.S. involvement in the League of Nations.