In 1963, the Post Office Department introduced the zip code. I’m not going to go into a lengthy explanation of how it works. Instead, let these fine, fine singers educate you:
In 1982, the USPS started using POSTNET — that’s the barcode made up of short and tall lines that you see in the lower left corner of most of your mail. POSTNET was first used in LA with the 5-digit zip code. In 1983, POSTNET was expanded to handle ZIP+4 codes (the Swingin’ Six needs to update their song). By 1984, there were over 250 OCR readers scanning POSTNET barcodes across the country, taking hourly mail processing from 1,7500 pieces to 6,200 pieces.