Final answer:
In 1991, the U.S. Postal Service issued a stamp to honor rock and roll musician Richie Valens, continuing their tradition of commemorating national figures and events.
Step-by-step explanation:
The U.S. Postal Service has a history of commemorating influential American figures and significant events through dedicated postage stamps. In 1991, a stamp was indeed issued to honor Richie Valens, a pioneering musician who made significant contributions to rock and roll music. Like other dedicated stamps, Valens' serves as a cultural recognition of his impact on music and American history. Stamps such as the special thermochromic ink stamp for the 2017 eclipse, the Salem Poor stamp as part of the Gallant Soldier series, and those commemorating figures like Margaret Mead or events like Expo '74 reflect Postal Service's tradition of embracing national heritage, accomplishments, and innovations.