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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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Montgomery County ZIP Codes

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

County State ZIP Code City Area Codes
Montgomery County MD 20830 Olney 240
Montgomery County MD 20832 Olney 227, 240, 301
Montgomery County MD 20833 Brookeville 227, 240, 301, 410, 443, 667
Montgomery County MD 20837 Poolesville 227, 240, 301, 571, 703
Montgomery County MD 20838 Barnesville 227, 240, 301
Montgomery County MD 20839 Beallsville 227, 240, 301
Montgomery County MD 20841 Boyds 227, 240, 301
Montgomery County MD 20842 Dickerson 227, 240, 301, 571, 703
Montgomery County MD 20847 Rockville 240
Montgomery County MD 20848 Rockville 240
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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.