ZIP Code 91310

91310 is one of California's ZIP codes, delivering to addresses in Castaic, Los Angeles County.

City: Castaic
County: Los Angeles County
State: California
Prefix: 913xx

Where this code sits

91310 is part of the 913xx range, the group of codes handled by one mail processing centre. Castaic is served by 2 ZIP codes in total.

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 91310 delivers to without sharing its boundary.

661 Area code 661

ZIP codes nearest 91310

The ZIP codes whose reference points sit closest to 91310.
ZIP code	Distance	Delivers to
ZIP code 91384	0.5 mi	Castaic, CA
ZIP code 91385	3.2 mi	Valencia, CA
ZIP code 91354	5.7 mi	Valencia, CA
ZIP code 91390	5.7 mi	Santa Clarita, CA
ZIP code 91355	7.4 mi	Valencia, CA
ZIP code 91381	7.7 mi	Stevenson Ranch, CA
ZIP code 91350	7.9 mi	Santa Clarita, CA
ZIP code 91380	8.1 mi	Santa Clarita, 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 91310, plotted from its record coordinates.

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

Scope ZIP code 91310. 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.