World War I patriotic cover mailed from Fort Riley, Kansas on March 11, 1918 with American flag machine cancel. Reverse bears imprint of the National War Work Council of the YMCA of the United States, “With the Colors,” the wartime YMCA program supporting American servicemen during WWI. Interesting military and home-front postal history item associated with one of America’s best-known Army training posts. 

Ships with protective sleeve

Postmark:  Fort Riley, Kansas 1918