In 1943 when a large number of postal employees were deployed to serve the military, the Post Office devised a system of zoning address to divide the country in 124 areas, from A-Z. In 1963, the department implemented a further system called Zoning Improvement Plan (ZIP) Code, which is the five digits code system we know as of today.
The ZIP code system benefited largely business mail that grew exponentially in the last 50 years, from the social correspondence in the past.
Today, with the usage of computers handling the bill payment system, bank deposits, and receipts, as well as social security and check that were once sent my mail, we should have expected the mail volume to decrease. Yet, the mail volume had increased over the years, with the development of new methods of distribution and logistics handling of packages to homes and business since Benjamin Franklin’s day.
The first two digits designate the broad geographical area in the United States, ranging from zero for the Northeast, to nine to the far West. This number is followed by two digits that pinpoint the population concentration and centers accessible to common transportation networks. The final two digits designate post offices.
At first, it was not mandatory, but in 1967, it was adopted by the public and business alike. Today, living in a certain ZIP code can add value to a home, as certain townships or neighborhoods are more desirable than others.