Chicago Tribune, April 6, 1917.

One hundred years ago today, April 6, 1917, the United States entered the First World War when Congress declared war on Germany.  President Wilson, in an address to a joint session of Congress on April 2, had asked for the declaration, citing unrestricted German submarine warfare and the Zimmermann telegram.  The Senate passed the resolution on April 4, with the House following on the morning of April 6.