I’m old enough to remember when ZIP Codes were never used on envelopes and parcel packages. As a boy, I learned that my address included the name of the city, the postal zone, and the name of the state. At that time, the last line of my address was Lincoln 2, Nebraska.
The last line of my address changed on July 1, 1963. We, along with the rest of the United States, were assigned a non-mandatory ZIP Code. The Post Office strongly recommended we use our specific five numbers on all mail. The last line of my address was altered to read, Lincoln, Nebraska 68502.
You might be interested in a little slice of US Postal Service history. In 1943, the Post Office Department (not yet called the US Postal Service) assigned postal zones for larger cities to help make mail delivery more efficient. For example, Lincoln was divided into several areas or zones. The particular number of each zone became part of the official address of each location in Lincoln. This is where Lincoln 2, Nebraska came from. Small towns did not have zone numbers because the town and its general vicinity were already a single postal subdivision. The last line of a small town address might be “Wahoo, Nebraska”.
In 1944, Robert Moon, a Post Office Department postal inspector proposed a three-digit system to describe postal territories or general post offices. The numbering was used only within the network of post offices and not used by the general public. This is when Lincoln, and its close vicinity were assigned the region code “685” for the main Lincoln Post Office. Hence, Mr. Moon has been credited with inventing the first three digits of the ZIP Code.
By the end of the 1950s, the Post Office Department realized that a more precise and public system would soon be needed in order to keep up with the growing population of the country. The department decided to modernize and consolidate their existing postal zones into a standardized number code system. The program became the ZIP Code system. ZIP is the acronym for “Zone Improvement Plan”.
They took Robert Moon’s internal three-digit regional numbers and added numbers to identify subdivisions within each region. For example, Wahoo, Nebraska Post Office already was assigned the internal number “680”. The new numbering system added two new numbers to identify a more specific area. The town would be identified with a new code of “66”. After July 1, 1963, Wahoo was assigned the ZIP Code of 68066.
In cities that already used zone numbers in the address, those zones became the last two digits of their ZIP Codes. Lincoln, Nebraska’s main Post Office was “685”. Each previous zone was added to “685”. So “Lincoln 2, Nebraska”, became “Lincoln, Nebraska 68502”.
By the 1980s, automation played a more important role in mail sorting and delivery. So the US Postal Service expanded the system to ZIP + 4. They took the basic ZIP Code and further divided the zone into smaller geographic segments such as a city block, office building, apartment complex, or post office box. A ZIP + 4 might look like “Wahoo, NE 68066-9998”.
There are now three more numbers that have been added to ZIP + 4. The combination is the “Postnet” barcode that is automatically added during the initial sorting process to the face of the mail item. The eleven digits system has further streamlined the USPS’s automation process.
So here’s the break down of a standard ZIP Code: The first digit stands for a set of particular states ie. Illinois, Missouri, Kansas, and Nebraska are “6”. The second number combined with the first is a region within that group, for example “68” and “69” are Nebraska. The third number identifies a main sorting post office. The last two numbers are the specific area like the small town or the former zone number.