ZIP Code 21770

21770 is one of Maryland's ZIP codes, delivering to addresses in Monrovia, Frederick County.

City: Monrovia
County: Frederick County
State: Maryland
Prefix: 217xx

Where this code sits

21770 is part of the 217xx range, the group of codes handled by one mail processing centre. It is the only ZIP code delivering to Monrovia.

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 21770 delivers to without sharing its boundary.

ZIP codes nearest 21770

The ZIP codes whose reference points sit closest to 21770.
ZIP code	Distance	Delivers to
ZIP code 21754	3.0 mi	Ijamsville, MD
ZIP code 21774	4.3 mi	New Market, MD
ZIP code 21771	4.8 mi	Mount Airy, MD
ZIP code 20872	5.5 mi	Damascus, MD
ZIP code 21704	7.2 mi	Frederick, MD
ZIP code 20871	7.9 mi	Clarksburg, MD
ZIP code 21701	8.0 mi	Frederick, MD
ZIP code 21762	9.1 mi	Libertytown, 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 21770, plotted from its record coordinates.

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

Scope ZIP code 21770. 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.