The following content comes direct from the DC DMV department:
DC DMV offers a commercial driver license (CDL) to professional drivers who reside in the District. The DC DMV CDL is a credential that complies with federal identification guidelines and can be used as a federal-level ID. It is valid for 8 years and can be renewed.
Driving a commercial motor vehicle (CMV) requires a higher level of knowledge, experience, skills, and physical abilities than driving a car or other non-commercial vehicle. To get a DC DMV CDL, you must pass both skills and knowledge testing geared to these higher standards. Additionally, as a DC DMV CDL holder, you will be held to a higher standard when you operate ANY type of motor vehicle on public roads.
To get a DC DMV CDL, you must:
More information on the DC.gov DMV website: http://dmv.dc.gov/service/obtain-commercial-driver-license