usps started using the extended zip+4 code in 1963.
when did the usps start using the extended zip+4 code?
1963
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". a zip+4 code uses the basic five-digit code plus four additional digits to identify a geographic segment within the five-digit delivery area, such as a city block, a group of apartments, an individual high-volume receiver of mail, a post office box, or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery. however, initial attempts to promote universal use of the new format met with public resistance and today the plus-four code is not required. in general, mail is read by a multiline optical character reader (mlocr) that almost instantly determines the correct zip+4 code from the address—along with the even more specific delivery point—and sprays an intelligent mail barcode (im) on the face of the mail piece that corresponds to 11 digits—nine for the zip+4 code and two for the delivery point.
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one current exception to this rule is the united states patent and trademark office (uspto). when the uspto was located in the crystal city neighborhood in arlington, virginia, it was assigned by the postal service the address "washington, dc 20231" despite being physically located in zip code 22202. however, the uspto now uses zip codes assigned to its current locations in alexandria, virginia. the patents side of the uspto uses a po box assigned the zip+4 code of 22313-1450 for all postal communications. the trademarks side of the uspto uses the same zip+4 code for most of its mail, but the office of the commissioner for trademarks has its own po box with the zip+4 code of 22313-1451, and some offices within that part of the uspto use the 22314 zip code.
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