ZIP Code 21139

21139 is one of Maryland's ZIP codes, delivering to addresses in Riderwood, Baltimore County.

City: Riderwood
County: Baltimore County
State: Maryland
Prefix: 211xx

Where this code sits

21139 is part of the 211xx range, the group of codes handled by one mail processing centre. It is the only ZIP code delivering to Riderwood.

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 21139 delivers to without sharing its boundary.

ZIP codes nearest 21139

The ZIP codes whose reference points sit closest to 21139.
ZIP code	Distance	Delivers to
ZIP code 21022	1.5 mi	Brooklandville, MD
ZIP code 21093	1.7 mi	Lutherville Timonium, MD
ZIP code 21204	2.4 mi	Towson, MD
ZIP code 21252	2.6 mi	Towson, MD
ZIP code 21284	2.6 mi	Towson, MD
ZIP code 21285	2.6 mi	Towson, MD
ZIP code 21209	2.9 mi	Baltimore, MD
ZIP code 21153	3.4 mi	Stevenson, 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 21139, plotted from its record coordinates.

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

Scope ZIP code 21139. 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.