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U.S. ZIP Codes Database 2026

Search by ZIP code, city, county, or state and find clear postal details with maps, time zones, and area code data.

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Williamson County ZIP Codes

Browse all ZIP Codes, cities, and associated area codes registered in Williamson County.

County State ZIP Code City Area Codes
Williamson County TX 78642 Liberty Hill 512, 737
Williamson County TX 78646 Leander 512
Williamson County TX 78651 Mc Neil 512
Williamson County TX 78664 Round Rock 512, 737
Williamson County TX 78665 Round Rock 512, 737
Williamson County TX 78673 Walburg 512
Williamson County TX 78674 Weir 512, 737
Williamson County TX 78680 Round Rock 512
Williamson County TX 78681 Round Rock 512, 737
Williamson County TX 78682 Round Rock 512
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About U.S. ZIP Codes

ZIP codes are a United States Postal Service system introduced in 1963 to make mail routing more accurate and efficient. The standard format uses five digits, while ZIP+4 adds four more digits for a more precise delivery segment.

ZIP codes cover the United States, its territories, military mail routes, and other USPS delivery points. This directory organizes that data for practical lookup by ZIP code, city, county, and state.