Last Line
The final line of a mailing address containing the city, state, and ZIP code, which the USPS uses as the primary field for initial mail routing.
In USPS terminology, the 'last line' refers to the bottom line of a domestic address: CITY, STATE ZIP (e.g., CHICAGO IL 60601). Automated mail processing starts by reading the last line to determine the destination sorting facility. If the barcode or OCR read of the last line is successful, the piece is routed immediately; the street address is read at a later stage for carrier route sorting.
USPS standards specify formatting rules for the last line: city name in full or approved abbreviation, 2-letter state code, and 5-digit (or 9-digit) ZIP code separated by specific spacing. Incorrect formatting can delay OCR reading and cause the piece to be diverted to manual processing.
For international mail, the last line contains the country name in the origin country's language or English, and the city/postal code format follows the destination country's conventions.