Title: United States
Content:   The United States remained neutral from the outbreak of World War I in 1914 until 1917 when it joined the war as an "associated power" alongside the Allies of World War I, helping to turn the tide against the Central Powers. In 1919, President Woodrow Wilson took a leading diplomatic role at the Paris Peace Conference and advocated strongly for the U.S. to join the League of Nations. However, the Senate refused to approve this and did not ratify the Treaty of Versailles that established the League of Nations. In 1920, the women's rights movement won passage of a constitutional amendment granting women's suffrage. The 1920s and 1930s saw the rise of radio for mass 
Title: United States in World War I
Content:   The United States declared war on Germany on April 6, 1917, nearly three years after World War I started. A ceasefire and Armistice was declared on November 11, 1918. Before entering the war, the U.S. had remained neutral, though it had been an important supplier to the United Kingdom, France, and the other powers of the Allies of World War I. The U.S. made its major contributions in terms of supplies, raw material, and money, starting in 1917. American soldiers under General of the Armies John Pershing, Commander-in-Chief of the American Expeditionary Force (AEF), arrived at the rate of 10,000 men a day on the Western Front in the summer of 1918. 
Title: Military history of the United States
Content:  The United States originally wished to remain neutral when World War I broke out in August 1914. However, it insisted on its right as a neutral party to immunity from German submarine attack, even though its ships carried food and raw materials to Britain. In 1917 the Germans resumed submarine attacks, knowing that it would lead to American entry. When the United States declared war in early April 1917, the United States Army was still small by European standards (most of which had conscription) and mobilization would take at least a year. Meanwhile, the United States continued to provide supplies and money to Britain and France, and initiated the first peacetime draft. Industrial mobilization 
Title: Diplomatic history of World War I
Content:  American entry into the war came in April 1917, after 2½ years of efforts by President Woodrow Wilson to keep the United States neutral.
Title: Axis &amp; Allies: World War I 1914
Content:  The United States may not enter the war until the beginning of round 4 unless it is attacked by a central powers player. The United States' Navy may also not leave sea zone 1
Title: United States in World War I
Content:  As late as 1917, the United States maintained only a small army, one which was in fact smaller than those of thirteen of the states already active in the war. After the passage of the Selective Service Act in 1917, it drafted 4 million men into military service. By the summer of 1918, about 2 million US soldiers had arrived in France, about half of whom eventually saw front-line service; by the Armistice of November 11 approximately 10,000 fresh soldiers were arriving in France daily. In 1917, Congress gave US citizenship to Puerto Ricans when they were drafted to participate in World War I, as part of the Jones Act. 
Title: United States in World War I
Content:  The American entry into World War I came on April 6, 1917, after a year long effort by President Woodrow Wilson to get the United States into the war. Apart from an Anglophile element urging early support for the British, American public opinion sentiment for neutrality was particularly strong among Irish Americans, German Americans and Scandinavian Americans, as well as among church leaders and among women in general. On the other hand, even before World War I had broken out, American opinion had been more negative toward Germany than towards any other country in Europe. Over time, especially after reports of atrocities 
Title: United States Navy operations during World War I
Content:  United States Navy operations during World War I began on April 6, 1917, after the formal declaration of war on the German Empire. The American navy focused on countering enemy U-boats in the Atlantic Ocean and the Mediterranean Sea, while convoying men and supplies to France and Italy. Because of United States' late entry into the war, her capital ships never engaged the German fleet, and few decisive submarine actions occurred.
Title: History of the United States (1865–1918)
Content:  The United States was remarkably unprepared for war in 1917, since it had not fought a major conflict since 1865. The military was small by modern standards and used out-dated weapons. A hasty expansion and modernization of the armed forces was thus launched. The draft began in spring 1917 but volunteers were also accepted. Four million men and thousands of women joined the services for the duration.
Title: United States World War I Centennial Commission
Content:  conflict. On April 6, 1917, Congress officially declared war against Germany and joined the Allied forces. Led by General John J. Pershing, the American Expeditionary Forces arrived in Europe in June 1917. American forces participated in several major battles, most notably the Meuse-Argonne offensive. This became a major turning point in the War, which had been at a stalemate for years. The War would finally end a year later on November 11, 1918. Over 4.7 million American men and women would serve, and more than 116,000 American soldiers, or "doughboys" as they were commonly referred to, would pay the ultimate sacrifice.

Question: when did the usa join world war one?
Answer: April 1917.
April 6, 1917.
in April 1917.