ZIP Code 78666

78666 is one of Texas's ZIP codes, delivering to addresses in San Marcos, Hays County.

City: San Marcos
County: Hays County
State: Texas
Prefix: 786xx

Where this code sits

78666 is part of the 786xx range, the group of codes handled by one mail processing centre. San Marcos is served by 2 ZIP codes in total; the full list, with the county each falls in, is on the San Marcos page.

San Marcos Texas ZIP codes →

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 78666 delivers to without sharing its boundary.

ZIP codes nearest 78666

The ZIP codes whose reference points sit closest to 78666.
ZIP code	Distance	Delivers to
ZIP code 78655	5.9 mi	Martindale, TX
ZIP code 78656	7.7 mi	Maxwell, TX
ZIP code 78670	10 mi	Staples, TX
ZIP code 78640	11 mi	Kyle, TX
ZIP code 78622	13 mi	Fentress, TX
ZIP code 78667	13 mi	San Marcos, TX
ZIP code 78130	13 mi	New Braunfels, TX
ZIP code 78676	15 mi	Wimberley, TX

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 78666, plotted from its record coordinates.

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

Scope ZIP code 78666. 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.