ZIP Code 21778

21778 is one of Maryland's ZIP codes, delivering to addresses in Rocky Ridge, Frederick County.

City: Rocky Ridge
County: Frederick County
State: Maryland
Prefix: 217xx

Where this code sits

21778 is part of the 217xx range, the group of codes handled by one mail processing centre. It is the only ZIP code delivering to Rocky Ridge.

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 21778 delivers to without sharing its boundary.

ZIP codes nearest 21778

The ZIP codes whose reference points sit closest to 21778.
ZIP code	Distance	Delivers to
ZIP code 21759	3.3 mi	Ladiesburg, MD
ZIP code 21775	3.4 mi	New Midway, MD
ZIP code 21788	3.7 mi	Thurmont, MD
ZIP code 21757	3.8 mi	Keymar, MD
ZIP code 21798	5.4 mi	Woodsboro, MD
ZIP code 21727	6.1 mi	Emmitsburg, MD
ZIP code 21793	8.8 mi	Walkersville, MD
ZIP code 21780	9.1 mi	Sabillasville, MD

Straight-line distance between place reference points, not driving distance. Where a place has no Census Gazetteer point, its postal centroid is used instead.

Each point is the reference point for 21778, plotted from its record coordinates.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Scope ZIP code 21778. Source GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated 15 July 2026. A ZIP code is a set of delivery routes, not an area; the point shown is a record coordinate, not a centre.