The USPS (United States Postal Service) utilizes ZIP codes as a part of the postal addresses. The purpose of using these ZIP codes is to speed up the direct mail distribution process even with the existence of a massive number of residential and commercial addresses. The term ZIP is the acronym for Zonal Improvement Plan which was implemented in USA way back in 1963. As per the records, Robert Moon, Philadelphia Postal Inspector, was the first person to propose the first 3-digit ZIP code to the Postmaster General.

Initially, the basic ZIP code format consisted of five digits; Moon’s 3-digit format combined with the 2-digit local zone numbers that were already in use. With the introduction of ZIP+4 in 1983, the number of digits increased into 9.

The Structure of ZIP+4

Compared to the basic version, ZIP+4 determines the destination with more accuracy. These newly added numbers represents respective streets or office buildings.

  • The first five digits (which appeared before 1983) determine the area of the country and the delivery office. So, the first five digits help direct mails to reach the respective delivery office initially. ZIP codes starts with zero represent the northeast regions in the country and the value increases towards the western regions. (the furthest ZIP codes from northeast, i.e. west, start with 9)
  • Sixth and seventh digits represent a delivery sector. Usually, it can be a set of blocks, a bunch of streets, a particular set of office buildings, a set of PO boxes, a large apartment, a large office building or even a small geographical area. With these two digits filter direct mails further.
  • Last two digits basically filter the mails according to the segments they are delivered. It can be a single floor of a particular building or a side of a certain street or even particular departments and PO boxes.

Although a vast majority of Americans were not ready to give this new system a warm welcome, authorities continued ZIP+4 realizing the long terms benefits it can deliver. With the implementation of this new system in 1983, the Government Accounting Office predicted a massive $5.26 billion saving for the next 16 years. In fact, with this new system,  the direct mail distribution system of the entire USA boosted significantly. Basically, direct mailing (the amount mailers spend on stamps) would cost considerably more, had ‘ZIP+4’ not been introduced by the USPS.

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