Washington D.C.
Requirements
U.S. citizen
Resident in DC for at least 30 days prior to the election day
You must be at least 16 years old (but cannot vote until 18 years old)
Not claim voting residence outside of the District of Columbia
Not be in jail for a felony conviction
Not have been found by a court to be legally incompetent to vote
https://www.vote4dc.com/ApplyInstructions/Register
Voter Registration Forms
Mail-in Ballot: All active voters will receive an mail-in ballot in the first week of October. The above link only needs to be used if you would like your ballot sent to a location other than your registered address.