PO Box ZIP Code
A ZIP code assigned exclusively to a range of Post Office Boxes at a particular USPS facility, separate from the street delivery ZIP code for the same area.
Many USPS facilities assign a distinct ZIP code to their PO Box lobby, different from the ZIP code used for carrier-delivered street addresses in the same town. For example, a small city might have ZIP 12345 for street delivery and 12346 for PO Boxes. This separation helps the USPS sort PO Box mail directly to the PO Box section without routing it through carrier routes.
PO Box ZIP codes are common in rural areas where many residents do not have street delivery and must pick up mail at the post office. In some cases, a PO Box ZIP code is the only ZIP code associated with a town.
Like unique ZIP codes, PO Box ZIPs generally have no residential population in Census data and are excluded from ZCTAs.