In Washington, D.C., a Living Will is referred to as a "Health Care Directive" and is included in an Advance Directive packet together with a form for naming a "Durable Power of Attorney for Health Care" (also known as a "Health Care Proxy") and specifying Organ Donation.

You and two (2) witnesses are required to sign your DC Advance Directive in order for it to be legal.
Washington, D.C. (District Of Columbia) Advance Directive Form