ZIP Code 91788

91788 is one of California's ZIP codes, delivering to addresses in Walnut, Los Angeles County.

City: Walnut
County: Los Angeles County
State: California
Prefix: 917xx

Where this code sits

91788 is part of the 917xx range, the group of codes handled by one mail processing centre. Walnut is served by 2 ZIP codes in total; the full list, with the county each falls in, is on the Walnut page.

Walnut California ZIP codes →

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 91788 delivers to without sharing its boundary.

ZIP codes nearest 91788

The ZIP codes whose reference points sit closest to 91788.
ZIP code	Distance	Delivers to
ZIP code 91789	0.6 mi	Walnut, CA
ZIP code 91792	1.9 mi	West Covina, CA
ZIP code 91748	3.2 mi	Rowland Heights, CA
ZIP code 91765	3.3 mi	Diamond Bar, CA
ZIP code 91791	3.6 mi	West Covina, CA
ZIP code 91744	4.2 mi	La Puente, CA
ZIP code 91723	4.7 mi	Covina, CA
ZIP code 91747	4.8 mi	La Puente, CA

Straight-line distance between place reference points, not driving distance. Where a place has no Census Gazetteer point, its postal centroid is used instead.

Each point is the reference point for 91788, plotted from its record coordinates.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Scope ZIP code 91788. Source GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated 15 July 2026. A ZIP code is a set of delivery routes, not an area; the point shown is a record coordinate, not a centre.