Today, Nov. 11, is Veterans' Day in the US. The date commemorates the signing of the Armistice that ended WWI, when Germany signed the Armistice on the 11th hour of the 11th day of the 11th month of 1918. President Woodrow Wilson first proclaimed an Armistice Day for November 11, 1919. The United States Congress passed a concurrent resolution seven years later on June 4, 1926, requesting the President issue another proclamation to observe November 11 with appropriate ceremonies. An Act (52 Stat. 351; 5 U. S. Code, Sec. 87a) approved May 13, 1938, made the 11th of November in each year a legal holiday; "a day to be dedicated to the cause of world peace and to be thereafter celebrated and known as 'Armistice Day'."
Other US legal documents from 20th Century wars:
April 2, 1917 President Woodrow Wilson's Joint Address to Congress Leading to a Declaration of War Against Germany (1917)
April 6, 1917 40 Stat. 1 Public Resolution 65-1 Joint Resolution: Declaring that a state of war exists between the Imperial German Government and the Government and the people of the United States and making provision to prosecute the same.
Dec. 8, 1941 President Franklin D. Roosevelt's Joint Address to Congress Leading to a Declaration of War Against Japan
Dec. 8, 1941 55 Stat. 795 Public Law 77-328 Joint Resolution: Declaring that a state of war exists between the Imperial Government of Japan and the Government and the people of the United States and making provisions to prosecute the same.
Aug. 7, 1964, 78 Stat. 384 Public Law 88-408 The Tonkin Gulf Resolution This joint resolution of Congress (H.J. RES 1145) authorized "all necessary measures to repel any armed attack against the forces of the UniteStates" and all steps necessary for the defense of U.S. allies in Southeast Asia. This gave President Lyndon Johnson authority to increase U.S. involvement in the war between North and South Vietnam.