| Letter | Description | Preceding Number? |
| 1-Adam 2-Adam |
Patrol (Northwest County: Clarksburg, Poolesville, Gaithersburg,
Darnestown, Rockville) Patrol (Potomac) |
Yes |
| 1-Baker 2-Baker |
Patrol (Northeast County: Damascus, Laytonsville, Brookeville,
Ashton) Patrol (Wheaton) |
Yes |
| 2-Charlie | Patrol (Silver Spring) | Yes |
| 2-Delta | Patrol (White Oak) | Yes |
| George | Wheaton Garages/Parking Detail | No |
| Henry | Equestrian | Yes |
| King | Canine | 9* |
| Lincoln | At-Large Patrol | No |
| Mary | Motorcycle (no longer used, now "Motor xx") | Yes |
| Sam | Supervisor (Sergeant) | No |
| Victor | Special Operations (Equestrian, Motor, etc.) when in cruisers | Yes |
| William | Watch Commander (Lieutenant) | No |
| Whiskey | Alcohol Enforcement** | 9 |
| X-ray | Citizen Volunteers*** | No |
* Canine units are numbered similarly to the County Police units. The Park Police's canine units are designated in 9-King-3x format, i.e., 9-King-31, 9-King-32, etc. (County Police canine units use 9-King-1x and 9-King-2x designations.)
** Used during County Police enforcement initiative, December 1998 and December 1999.
*** Citizen volunteers patrol parks and report suspicious activity, etc.