ZIP+4 and DPC explained, Gary Sanders, Logics Solutions These extra four digits divvy up a ZIP code region into blocks and segments, where blocks usually denote a specific side of a street or even a large building and a segment indicates a smaller portion of that block, possibly even a specific floor of a building. ZIP+4 after a prolonged push-back from Congress back in 1983, twenty years after the original ZIP codes were introduced. But the Postal Service has never come close to allocating all 100,000 codes, and only about 40,000 ZIP codes are ever actively allocated at any give time, although the Postal Service periodically adds or deletes ZIP codes as needed.įor even more precise categorization of locations and sorted mail, the US Postal Service rolled out a nine-digit By the time ZIP codes were introduced in 1963, that number was down to 34,498. That limit on the number of available codes has never been a problem so far since the number of post offices in the US peaked in 1901 with 76,945. The Daily Herald (Provo, Utah), July 7th 1963Ī 5-digit ZIP code comprised of the numbers 0-9 only has 100,000 possible codes available, ranging from 00000 to 99999.

Bentley Hahn that would become the 5-digit ZIP code. But it would take some twenty years for Postmaster General Edward Day, faced with a rising sea of business mail that was inundating post offices around the country in the 1960’s, to recognize the potential value of these coding schemes, combining the older 2-digit and 3-digit ideas in a newly devised plan by postal inspector A year later, a Postal Inspector in Philadelphia, Robert Moon, suggested a 3-digit code scheme that would expand this concept. The ZIP code was an extension of 2-digit “postal codes” that were introduced in 1943 to a limited number of major cities, specifically intended to help inexperienced postal workers during a skilled labor shortage caused by World War II. The 5-digit codes were aimed at improving the efficiency and accuracy of how mail was processed and sorted, breaking up the country into different geographic zones with a manageable set of numbers. ZIP, codes were first introduced by the US Postal Service in 1963. But do you have any idea what the size or shape of your ZIP code looks like? And do you know the extent to which your ZIP code defines you? ZIP Codes I’ll assume you can picture the rough outline of the state that you live in as well as the general boundary of your city or town, within a reasonable approximation. You hopefully know where your house number is (that’s where you live), and you can probably picture the length of your street easily enough. Think about your own address in your head. Addresses are funny things when you start to think about them too much.

Us zip code history