This measure, introduced by Marion Barry, the city's Mayor, to control the behaviour of teenagers, means that Washington joins the other 150 US cities, which have restricted the movements of young people to try to cut violent crime. "We believe our young people ought to be safe from handgun violence and violent assaults," says Mayor Barry.
The police are taking a lenient approach at first. Violating the curfew, like other juvenile offences, is not a crime and will not leave the offender with a criminal record.
The first time a young person is picked up, the only likely result will be a requirement for the whole family to attend counselling.
Subsequent violations, however, could leave the parents with a fine of up to $500 (Pounds 312). They may also be required to attend parenting classes. Adults involved in curfew infringements may be required to do community service.
But the new ordinance has so many exceptions, according to some observers, that any quick-thinking youth will be able to avoid being sent to one of the three curfew centre. Exceptions will be granted for those who are accompanied by a parent or guardian, or who are running an errand, working, travelling from work, involved in an emergency, attending a religious or recreational event, or exercising any right under the First Amendment (the right to free speech).
The curfew will operate from midnight to 6am during the summer. During the school year, it will begin at 11pm on week nights.
Curfews are not new. They were used in America at the turn of the century to curb rising crime among immigrant youth, and again during World War II to help parents who were busy with the war effort.
Recently the Supreme Court gave a boost to the new popularity of teen curfews by refusing to hear a constitutional challenge to the 1991 law in Dallas.
It is not stopping lawsuits, however. The American Civil Liberties Union has said it will challenge the new Washington curfew in the courts. Arthur Spitzer, ACLU legal director in the Washington area, said: "Our main concern is that this is a free country. People have the right to stand outside, look at the stars, talk to their neighbour or walk to the store for milk."
But the new curfew has the support of the general public, including many young people, who hope it will save lives. Only three days before the new rule took effect, a 14-year-old girl was shot dead on a Washington street corner at 12.40am.