U.S. postal lookup

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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Union County ZIP Codes

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

County State ZIP Code City Area Codes
Union County SD 57038 Jefferson 402, 531, 605, 712
Union County SD 57049 North Sioux City 402, 531, 605, 712
Union County TN 37779 Luttrell 865
Union County TN 37807 Maynardville 423, 865
Union County TN 37866 Sharps Chapel 423, 865
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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.