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Zip Code 21778 — Rocky Ridge, MD

ZIP Code 21778 is associated with Rocky Ridge, MD, in Frederick County. The listed population estimate is 745; estimated density is 15.8 people per square mile. Among records with population estimates, it ranks #21 of 27 in Frederick County and #369 of 470 in MD.
Page generated: 2026-10-08. This is not the source data release date.

📍 View location on OpenStreetMap (39.615760, -77.337540)

Data MetricLocal Statistic
Postal / Zip Code21778
Primary CityRocky Ridge
State / ProvinceMD
CountyFrederick
Total Population745
Population Density15.8 people/sq mi
TimezoneAmerica/New_York

How 21778 Compares

MetricZIP 21778Frederick County recordsMD records
Population estimate745300,100 (sum)6,205,597 (sum)
Population Density15.8 /sq mi----
County population rank#21 of 27----
State population rank#369 of 470----

Regional sums combine the population estimates in the listed ZIP records; they are not official county or state population totals.

Explore More ZIP Codes

Nearby ZIP Codes in MD

ZIP CodeCityDistancePopulation estimate
ZIP 21757Keymar4.3 mi2,671
ZIP 21788Thurmont4.6 mi11,654
ZIP 21727Emmitsburg5.0 mi6,052
ZIP 21798Woodsboro5.7 mi2,928
ZIP 21780Sabillasville8.1 mi2,159

Data Sources & Methodology: Geographic coordinates and ZIP Code assignments are derived from underlying geographic and postal datasets. Note that ZIP Codes are USPS postal delivery areas, while Census ZCTAs are statistical approximation areas. Read full methodology →