The Treaty of Versailles was signed on June 28, 1919, marking the official end of World War I. Nonetheless, the armistice date of November 11, 1918, remained in the public imagination as the date that marked the end of the conflict.
One year later, in November 1919, U.S. President Woodrow Wilson proclaimed November 11 as the first commemoration of Armistice Day. The day’s observation included parades and public gatherings, as well as a brief pause in business and school activities at 11 a.m.
On November 11, 1921, an unidentified American soldier killed in the war was buried at Arlington National Cemetery near Washington, D.C. On the same day the previous year, unidentified soldiers were laid to rest at Westminster Abbey in London and at the Arc de Triomphe in Paris.
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Red poppies, a symbol of World War I from their appearance in the beloved poem "In Flanders Fields" by John McCrae, are sold in Canada and the United Kingdom on Remembrance Day to raise money for veterans or worn in the lapel as a tribute.
On June 4, 1926, Congress passed a resolution that the “recurring anniversary of [November 11, 1918] should be commemorated with thanksgiving and prayer and exercises designed to perpetuate peace through good will and mutual understanding between nations,” and that the president should issue an annual proclamation calling for the observance of Armistice Day.
By that time, 27 state legislatures had made November 11 a legal holiday. An act approved May 13, 1938 made November 11 a legal Federal holiday, “dedicated to the cause of world peace and to be hereafter celebrated and known as ‘Armistice Day.'”
In actuality, there are no U.S. national holidays because the states retain the right to designate their own, and the government can only designate holidays for federal employees and for the District of Columbia. In practice, however, states almost always follow the federal lead.
Source : http://www.history.com/topics/holidays/history-of-veterans-day