The United States entered World War I on April 6, 1917 when Congress voted to declare war on Germany. U. S. forces, known as the American Expeditionary Forces, were under the command of Army General John J. Pershing.

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The armistice was signed by Germany on November 11, 1918. A formal state of war between the two sides persisted for another seven months, until the signing of the Treaty of Versailles with Germany on June 28, 1919. 

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The total number of WWI veterans with uniforms currently on display is 23.