ZIP Code - Background

Background

The United States Post Office Department (USPOD) implemented postal zones for large cities in 1943. For example:

Mr. John Smith

3256 Epiphenomenal Avenue

Minneapolis 16, Minnesota.

The "16" was the number of the postal zone within the city.

By the early 1960s a more organized system was needed, and on July 1, 1963, non-mandatory ZIP codes were announced for the whole country. Simultaneously with the introduction of the ZIP code, two-letter state abbreviations were introduced. These were to be written with both letters capitalized. The reason for the two-letter abbreviations is that it was thought that a long city name coupled with a multi-letter state abbreviation (e.g. Mass. for Massachusetts; Ca., Cal., or Calif. for California; Pa., Penn., or Penna. for Pennsylvania) would be too long for address labels used on magazines when the ZIP code was added. Robert Moon, an employee of the post office, is considered the father of the ZIP code; he submitted his proposal in 1944 while working as a postal inspector. The post office gives credit to Moon for only the first three digits of the ZIP code, which describe the sectional center facility (SCF) or "sec center." An SCF is a central mail processing facility with those three digits. The SCF sorts mail to all post offices with those first three digits in their ZIP codes. The mail is sorted according to the final two digits of the ZIP code and sent to the corresponding post offices in the early morning. Sectional centers do not deliver mail and are not open to the public (though the building may include a post office open to the public), and most of the workers are employed to work night shift. Mail picked up at post offices is sent to their own SCF in the afternoon, where the mail is sorted overnight. In the cases of large cities, the last two digits coincided with the older postal zone number, thus:

Mr. John Smith

3256 Epiphenomenal Avenue

Minneapolis, MN 55416

In 1967, these were made mandatory for second- and third-class bulk mailers, and the system was soon adopted generally. The United States Post Office used a cartoon character, whom it called Mr. ZIP, to promote use of the ZIP code. He was often depicted with a legend such as "USE ZIP CODE" in the selvage of panes of stamps or on labels contained in, or the covers of, booklet panes of stamps.