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Zip Code 20878 — Gaithersburg, MD

ZIP Code 20878 is associated with Gaithersburg, MD, in Montgomery County. The listed population estimate is 66,115; estimated density is 1,248.3 people per square mile. Among records with population estimates, it ranks #2 of 46 in Montgomery County and #3 of 470 in MD.
Page generated: 2026-10-08. This is not the source data release date.

📍 View location on OpenStreetMap (39.113760, -77.247810)

Data MetricLocal Statistic
Postal / Zip Code20878
Primary CityGaithersburg
State / ProvinceMD
CountyMontgomery
Total Population66,115
Population Density1,248.3 people/sq mi
TimezoneAmerica/New_York

How 20878 Compares

MetricZIP 20878Montgomery County recordsMD records
Population estimate66,1151,076,754 (sum)6,205,597 (sum)
Population Density1,248.3 /sq mi----
County population rank#2 of 46----
State population rank#3 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 20899Gaithersburg2.7 mi57
ZIP 20874Germantown2.9 mi62,738
ZIP 20877Gaithersburg3.7 mi38,546
ZIP 20850Rockville3.9 mi50,353
ZIP 20880Washington Grove4.3 mi577

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 →