Not many people realize this, but the Zip Code system did not become mandatory for the bulk of mail until 1967. To ramp up the initiative and to get the public ready for using them the US Post Office launched a campaign to educate the public. To do this they introduced a new character Mr. Zip, posted his visage and the Zip Code message just about everywhere and even pulled in Ethel Merman to do commercials.
They also enlisted The Swingin’ Six to appear in an education/informational film release during the 1960s. It was in this film that the Zip Code Song appeared. The song is, well, very sixties, and it is better watched than described.
For those who are interested, The Swingin’ Six were a folk/pop group, whose members were Steve Burnett, John Fisher, John Patrick Lanigan, Richard Nieves, Ann Rachel and Carol Richards (they even had and album). It might not be the type of music you will listen to every day, but I think it might put a smile on your face if you give it some time.