District of Columbia Mayor Vincent Gray has signed a bill that decriminalizes possession of up to an ounce (28 grams) of marijuana in the U.S. capital, a spokeswoman said.
The law makes possession a civil violation with a penalty of $25, lower than most city parking tickets. Possession had been a misdemeanor carrying up to six months in jail and a $1,000 fine.
Proponents had backed the measure as an issue of fairness.
A study by the American Civil Liberties Union had shown that blacks in Washington were eight times more likely to be arrested for pot than people of other races.