"The poster was initially produced by the Ministry of Information in 1939 during the beginning of World War II. It was intended to be distributed in order to strengthen morale in the event of a wartime disaster. Two-and-a-half million copies were printed, although the poster was distributed only in limited numbers. The designer of the poster is not known.
P.S. If you actually want to check out some of the things you can buy.. look at Etsy (my favorite website!) "Keep Calm and Carry On" on Etsy!