In the beginning, there was the dummy. Long before Dora the Explorer, children's television was dominated by a freckly marionette and his pal Buffalo Bob. Howdy Doody's template--a vaudevillian romp full of wacky characters and make-believe--was followed well into the 1960s, picked up by shows like Captain Kangaroo and Bozo's Circus. (Before syndication, early children's programs were franchised across the country; at one time there were more than 200 Bozo the Clowns working U.S. airwaves.)
But while these shows were fun, they were far from educational. It wasn't until the debut of Sesame Street on Nov. 10, 1969, that TV became a medium tasked with developing young minds. Sesame Street's success wasn't exactly a surprise--about 2 million households tuned in to its premiere on PBS--but it was groundbreaking nonetheless. In addition to teaching kids ABCs and math--under the tutelage of an 8-ft.-tall yellow bird and an irritable garbage-can dweller--it was one of the first TV shows to depict an inclusive, racially harmonious neighborhood, prompting Mississippi to ban it (briefly) in 1970. Forty years later, Sesame Street is shown in more than 140 countries and is the longest-running kids' program in U.S. history.
While Sesame Street inspired a new approach to children's programming, other formats were faltering. Sitcoms like Gilligan's Island began to push out locally produced kids' shows, while animation studios like Hanna-Barbera offered their own distractions. In 1990 the Children's Television Act required that all stations air at least three hours of educational programming a week, prompting a brainteasing revolution. Preschool kids now learn problem-solving from Blue's Clues, teamwork from Wonder Pets! and Mandarin from Ni Hao, Kai-lan. Good thing they already know how to get to Sesame Street.