In which county is ZIP code 21139 located?

ZIP 21139 is listed under Baltimore County, MD.

When was this page updated?

This page was updated on 2026-01-08.

ZIP Code 21139: Riderwood, MD

ZIP: 21139

County: Baltimore County

Coordinates: 39.40930, -76.64860

ZIP Type: Standard

Time Zone: Eastern Time (ET)

Get a reliable snapshot of the Riderwood, MD postal area 21139. This page summarizes county, coordinates, and local facts to help with services and location research.

Primary City	Riderwood
ZIP Code	21139
County	Baltimore County
State	MD
Latitude / Longitude	39.40930, -76.64860
ZIP Type	Standard
Time Zone	Eastern Time (ET)
Data Updated	2026-01-08

Maps & Useful Links

Open in Maps: Google Maps · OpenStreetMap

These links show the approximate center point for ZIP 21139 (not an exact boundary).

Geographic & Administrative Context

For mapping and verification, 21139 is commonly represented around 39.40930, -76.64860. These coordinates help identify the general area within Baltimore County, MD.

Local Coverage Notes

ZIP codes can cover multiple neighborhoods and unincorporated areas. Use ZIP 21139 for mail delivery and general location reference in Baltimore County, MD.

Coverage may include nearby neighborhoods and adjacent unincorporated areas commonly associated with Riderwood.

Related ZIP Codes (Nearby)

Explore other postal codes near Riderwood within MD.

Frequently Asked Questions

What is the primary city for ZIP code 21139?

The primary city for this ZIP code is Riderwood, located in MD.

In which county is 21139 located?

ZIP code 21139 is situated within Baltimore County, MD.

What are the coordinates for 21139?

The approximate center point is 39.40930 (Latitude) and -76.64860 (Longitude).

Is ZIP code 21139 active?

This page lists ZIP 21139 as Listed based on the latest refresh date shown above.

Does ZIP 21139 cover multiple areas?

Yes. Many ZIP codes cover multiple neighborhoods or nearby areas. For exact boundaries, use official mapping tools.

Methodology & Data Notes

How we build this page: We generate this page from a structured ZIP dataset and refresh key fields (city, county, and coordinates) during scheduled updates. Coordinates represent an approximate center point, not an official boundary map.
Sources: Public ZIP reference datasets and geographic coordinate references. If you use specific sources (e.g., USPS, Census), list them on your About/Methodology page.

Page updated: 2026-01-08