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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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Alameda County ZIP Codes

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

County State ZIP Code City Area Codes
Alameda County CA 94501 Alameda 341, 415, 510, 628
Alameda County CA 94502 Alameda 341, 510
Alameda County CA 94536 Fremont 341, 510, 925
Alameda County CA 94537 Fremont 510
Alameda County CA 94538 Fremont 341, 408, 510, 669
Alameda County CA 94539 Fremont 341, 408, 510, 669, 925
Alameda County CA 94540 Hayward 510
Alameda County CA 94541 Hayward 341, 510
Alameda County CA 94542 Hayward 341, 510
Alameda County CA 94543 Hayward 510
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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.