Publication 28 - Postal Addressing Standards > 2 Postal Addressing Standards > 22 Last Line of the Address
It is strongly recommended that addresses use only approved Last Line (city) names as described in the Postal Service City State file currently in effect.
City names with the City State Mailing Name indicator flag set to YES in the City State file are considered part of a complete and standardized address; city names with the flag set to NO in the City State file should not be used in a complete and standardized address. For a complete and standardized address, abbreviations for city or state names must be shown in the Postal Service City State file. If you are preparing prebarcoded mail, city names set to NO for mailing name can be used.