ALT On This Day, on May 6, 1840, the famous Penny Black became officially valid for use in Great Britain, marking a revolutionary moment in communication history. The Penny Black was the world’s first adhesive postage stamp used in a public postal system. Although it was first issued on May 1, 1840, it became officially valid for postal use on May 6. The stamp featured a profile portrait of young Queen Victoria based on a sketch by William Wyon. Its simple black design included the words “POSTAGE” and “ONE PENNY,” making it both recognizable and difficult to counterfeit at the time. In 1837, British postal rates were expensive, confusing, and inconsistent. To solve the problem, English reformer Sir Rowland Hill proposed a prepaid adhesive stamp system that would simplify mail delivery and make communication affordable for ordinary people. The Penny Black allowed letters weighing up to half an ounce (14 grams) to be delivered anywhere in Great Britain for a flat rate of just one penny.