It seems like almost yesterday that the US postal system implemented a zone improvement plan for distribution of the United States mail. World War II had dramatically increased the volume of mail and in 1943 a series of basic postal zones were created. But by the 1960’s the character and volume of U.S. mail dramatically changed. There was a virtual explosion of business mail. By 1963 business transactions made up 80%of the total volume. Computers created a massive centralization of business