ZIP Codes are a system of postal codes used by the United States Postal Service since 1963. The term ZIP, an acronym for Zone Improvement Plan, was chosen to suggest that the travels more efficiently, and therefore more quickly. The basic format consists of five numerical digits, an extended ZIP+4 code, introduced in 1983, includes the five digits of the ZIP Code, a hyphen, and four additional digits that determine a more specific location within a given ZIP Code. The term ZIP Code was originally registered as a servicemark by the U. S. Postal Service, USPS style for ZIP is all caps and the c in code is also capitalized, although style sheets for some publications use sentence case or lowercase. The early history and context of postal codes began with postal district/zone numbers, the United States Post Office Department implemented postal zones for numerous large cities in 1943. For example, Mr. John Smith 3256 Epiphenomenal Avenue Minneapolis 16, by the early 1960s a more organized system was needed, and on July 1,1963, non-mandatory five-digit ZIP Codes were introduced nationwide. Three months later, on October 1,1963, the U. S, an earlier list in June had proposed capitalized abbreviations ranging from two to five letters. The abbreviations have remained unchanged, with one exception, according to the historian of the U. S. 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 only for the first three digits of the ZIP Code, which describe the sectional center facility 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, Mail picked up at post offices is sent to their own SCF in the afternoon, where the mail is sorted overnight. The United States Post Office used a character, which it called Mr. ZIP. He was often depicted with a such as USE ZIP CODE in the selvage of panes of stamps or on labels contained in, or the covers of. In 1983, the U. S. Postal Service introduced an expanded ZIP Code system that it called ZIP+4, often called plus-four codes, add-on codes, or add ons. But initial attempts to promote use of the new format met with public resistance. For Post Office Boxes, the rule is that each box has its own ZIP+4 code. However, there is no rule, so the ZIP+4 Code must be looked up individually for each box. It is common to use add-on code 9998 for mail addressed to the postmaster,9999 for general delivery, for a unique ZIP Code, the add-on code is typically 0001
A 1963 U.S. Post Office sign
U.S. postage stamp, 1973: "It all depends on ZIP Code"