Geographic boundaries of U.S. Postal Service five-digit ZIP Code areas from HERE, aligned to the street centerlines of the Q2 2018 HERE core map release.

HERE (the company that now includes data products that were formerly branded as "Navteq") maintains several versions of postal code data. The version distributed by MassGIS is an extract of HERE's nationwide "Un-generalized, High Definition, with County" layer. Relative to HERE's standard Postal Code Boundaries product, a significant amount of line work was created for this HD version to better segregate delivery to adjacent ZIP codes. The HERE Map line work was still used as much as possible. Boundaries have increased detail to more closely reflect postal code delivery. In this HD version, multi-part ZIP Code boundaries are allowed more often, when needed to reflect non-contiguous postal delivery. This dataset displays water features on coastlines but does not include "holes" for inland water bodies, and includes ZIP Code boundaries split at County boundaries.

The HERE Postal Code Boundaries product does not have void areas in postal coverage, even if such non-delivery areas exist in reality (such as a remote mountainous area). This is by design, for aesthetic purposes and to ensure that a postal code is assigned to all geographic areas.

MassGIS made minor edits to a few ZIP Code boundaries in Boston based on address data from the city. MassGIS also projected the data into the Massachusetts State Plane Mainland coordinate system.