Day Explains

Numeric System Needed

As a result, the evaluation and decision-making was narrowed down to a numeric code of some sort – an approach which was promising because a simple two digit code (the familiar local zone number) – had been used successfully in over a 100 large cities for more than 20 years. Particularly promising was the fact that an amazingly high percentage of mail in these communities was zoned – or coded in spite of the fact that promotional efforts on zone numbers had been minimal in the last 10 years. 

The proposed numerical codes ran a gamut from simple routing codes which would have limited use in the overall mail system to highly sophisticated and extremely complex codes which would earmark a letter right down to the individual carrier route. 

The first extreme was rejected not being broad enough nor of sufficient promise to justify the work required of the mailer and the Department, and the second was deferred because it required equipment beyond the present state of the art and the potential annual adjustment of thousands of carrier routes to serve more than one million additional addresses each year. 

The result is ZIP Code – Zoning Improvement Plan – which will continue to utilize the familiar local zone number in the 109 cities so coded for many ears, add local zoning to a hundred or more additional cities. Establish individual codes for all other communities in the United States through their local post offices—and prefix each delivery area number with the three-digit sectional center code. 

ZIP Code merely extends exactly the same pattern as local zoning to the entire United States. It breaks down the whole country into a pattern of service areas – by numbering each one by national area. Sectional center, and local zone or delivery post office. 

553 Sectional Centers

But perhaps the most significant fact overlooked by large users of the mail system in examining the ZIP Code is the basic importance of the establishment of 553 sectional centers whose three-digit numerical designations serve as the prefix for all ZIP Code numbers. 

These offices (manual adjustments within the structure for operational and transformational reasons will be updated annually) are now for all practical purposes the major concentration centers for the “massing” of both incoming and outgoing mail between and points of the United States. The sectional centers have been chosen on the basis of their convenience to major transportation arteries, their relation to surrounding officers, available facilities and their position in the density pattern of mail throughout the country. 

While no change of any consequence will be felt immediately in the operation or personnel of the other 35,000 officers, we can now concentrate our efforts at these relatively few key points in developing major future improvements in service, mechanization and efficiency.

Each of these sectional centers serves an average of 77 surrounding offices, automatically providing built-in extension for the coding pattern anticipation future population growth and development of the economy in all parts of the country. In other words, the sectional center with the first three digits 000 can ultimately serve the local post offices numbered from 000(00) to 000(99), for a total of 100 delivery areas or local post offices. 

Room for Expansion

Beyond that point, you will notice in the overall sectional center pattern that certain three-digit prefixes seem to be missing. These numbers in the sequence have been deliberately left out to provide for the establishment of new sectional centers in future years, when and if population and mail volume growth warrant. 

The revolutionary character of this conception should be obvious. Instead of spreading our modernization efforts thinly among 35,000 post officers. We can now concentrate them on roughly 530. With the impact in those offices touching literally the entire mail stream of the United States. 

Immediately, the code has enormous potentials. First and foremost, it does provide a logical and effective way for the Post Office Department and large mailers, together, to utilize the ADP equipment which is in use in large mailing establishments throughout the United States for the preparation of mail. The inclusion of the five-digit ZIP Code as the “last word in mail addressing.” That is, following the city and state designation in all addresses, will make presorting much easier, faster and more effective before it ever leaves the mailer’s shop. 

In the post office, the numerical code provides a sure and easy sorting method to short-cut handling and to cut down on errors in the handing of mail between origin and destination without unreasonable demands on human memory schemes. In the case of large mailings, the Code will permit presorted mail to move directly from sectional center to sectional center without additional prepackage handling at intervening points. It is compatible with transportation routing codes. In many industries the Code will be a short-cut to spot mailings and regional mailings to specific areas of the country. 

Many useful Suggestions

Originally this application – the use of the ZIP Code only by large volume mailers with ADP equipment – was our goal. However, the reaction to the coding plan, first announced last November and detailed in late April, was amazingly good. Large mailers responded with considerable interest. There were useful suggestions and an amazingly high degree of indicated cooperation. The press and the public did not, as many anticipated, react unfavorably or negatively to the coding proposal. 

As the plan was developed, we raised our sights slightly and aimed for the use of the ZIP Code in return addresses by the general public. Incidentally, this proposal resulted from suggestions made by large mailers who pointed out that, while they were willing to code their existing mailing lists, there would be problems in keeping the lists up-to-date without such return address cooperation on the part of the public. Again, reaction was good and better than many people had expected.