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.

42,735 verified records
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State directory

Illinois ZIP Codes

Complete postal directory, details, and geographic map for the State of Illinois.

State ZIP Code City County Area Codes
IL 60548 Sandwich DeKalb County 331, 630, 779, 815
IL 60549 Serena LaSalle County 779, 815
IL 60550 Shabbona DeKalb County 779, 815
IL 60551 Sheridan LaSalle County 779, 815
IL 60552 Somonauk LaSalle County 779, 815
IL 60553 Steward Lee County 779, 815
IL 60554 Sugar Grove Kane County 331, 630
IL 60555 Warrenville DuPage County 331, 630
IL 60556 Waterman DeKalb County 779, 815
IL 60557 Wedron LaSalle County 779, 815
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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.