How do I buy medical cannabis in Washington, D.C.?

It is only legal to purchase cannabis in Washington, D.C. if you have a medical cannabis card.  
There are currently seven licensed dispensaries in DC.
The allowed product types include flower, concentrates, edibles, topics, and cartridges. The sale of transdermal products, seeds, and seedlings is illegal.

The licensed dispensaries are:

National Holistic Healing Center

National Holistic Healing Center
1718 Connecticut Ave. T300 
Washington, DC 20009
(202) 618-5635

Takoma Wellness

Takoma Wellness
6925 Blair Road NW
Washington, DC 20012
(202) 465-4260

Capital City Care

Capital City
1115 U Street NW
Washington, DC 20009
(202) 292-5071

Herbal Alternatives

Herbal Alternatives  
1710 Rhode Island Avenue, NW 
Washington, DC 20036
(202) 618-5635

Kinfolk Dispensary

KINFOLK Dispensary
433 Massachusetts Avenue NW
Washington, DC 20001
(202) 758-3795

Cannabliss

Cannabliss
4721 Sheriff Rd NE
Washington, DC 20019
(202) 388-3000

Anacostia Organics

2022 Martin Luther King Jr Ave. SE
Washington, DC 20020
(202) 845-8574