ZIP Code 21139 is located in Riderwood Maryland. 21139 is entirely within Baltimore County. Regionally, it is located in Metro Baltimore.
| ZIP Code Name | Riderwood |
| Primary County | Baltimore County |
| ZIP Code Type | PO Box |
| Current Time | EDT |
| Coordinates | 39.39298630,-76.58477783 |
| Adjacent ZIP Codes | |
| Region | Metro Baltimore |
| Metropolitan/Micropolitan Stat Area | Baltimore-Columbia-Towson, MD |
| Time Zone | Eastern Daylight Time |
| IANA Timezone | America/New_York |