The United States entered World War I when Congress declared war on Germany on April 6, 1917, almost two years after the Great War began on the European continent and at sea.The postmark was issued on 22nd April 2017 during stamp show held by the Kalamazoo Stamp Club in Kalamazoo, Mich.
The artwork on the square or diamond-shape postmark shows a WWI-era biplane in flight with rocky peaks in the background. Three stars are featured in the upper point of the postmark. The inscription commemorates “U.S. ENTRY WW1,” and “100th anniversary station” in Comstock, Mich.