Forty years ago this week, America found its way to "Sesame Street" and discovered that entertaining and educating children didn't have to be mutually exclusive.

Joan Ganz Cooney and Lloyd Morrisett of the Children's Television Workshop created "Sesame Street" as an educational mission to low-income children who watched more television and read fewer books than their middle-class and affluent peers.

Using television to educate children was considered a radical idea at the time. "Sesame Street's" resident puppeteer, Jim Henson, designed a menagerie of flawed, but lovable characters he called Muppets to interact with the show's human actors and guest stars who came in as many types and colors as the puppets themselves.

Debuting the year after Martin Luther King's assassination, "Sesame Street" featured African-American regulars Gordon (Hal Miller) and Susan (Loretta Long), who were equal to the show's white characters in every way. This was such a scandalous idea in 1969 that Mississippi refused to air the show for nearly two weeks. With "Sesame Street," many American children got their first view of what a colorblind society looks like.

Children all over the world learned to spell and count with Big Bird, Count von Count, Oscar the Grouch, Elmo, Cookie Monster, Kermit the Frog, Miss Piggy and Bert & Ernie.

In this country, the Educational Testing Service reported that children who watched the show regularly during its first year experienced a 62 percent increase in cognitive skills. Parents, social scientists and teachers fell over each other praising the show. Though middle-class kids weren't "Sesame Street's" original target audience, they were among its biggest beneficiaries.

Over the years, the show examined adult issues including divorce and death. In 2003, it introduced an HIV-positive Muppet. Media personalities, artists and politicians treat an invitation to appear on "Sesame Street" as high an honor as being a guest on "The Simpsons." This week, first lady Michelle Obama visited the show and President Obama taped a message honoring the long-running series.

After 40 years Big Bird and Oscar the Grouch have friends in very high places.

Cartoonist Rob Rogers does "Rob's Rough," an early look at his work and his creative process, exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.