Address unknown

Yesterday at break while reading Time magazine, I saw a blurb about the US Post Office putting zip codes into place in 1963. When I mentioned it to Carolyn, she asked what they did before that. I tried to kick-start the old brain, because I knew that there was a song which mentioned the previous system. All that came to mind was "Please Mr. Postman" but I knew that wasn't it. So, I was forced to Google and learned that for 20 years pre-63, the PO used zones (usually one or two digit numbers.) And then the light bulb lit. In the Elvis song "Return to Sender" he sings:


Return to sender, address unknown.
No such number, no such zone.