People roll joints at a marijuana party near the University of California at Berkeley campus in Berkeley, Calif, in 1966. In 2012, Washington state and Colorado voted to legalize and regulate its recreational use. But before that, the plant, renowned since ancient times for its strong fibers, medical use and mind-altering properties, was a staple crop of the colonies, an "assassin of youth," a counterculture emblem and a widely accepted — if often abused — medicine.

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In 1972 a commission appointed by President Richard Nixon to study marijuana said it should be decriminalized and regulated. Nixon rejected that, but a dozen states in the 1970s went on to eliminate jail time as a punishment for pot arrests.

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People attending an Amendment 64 watch party celebrate after a local television station announced the marijuana amendment's passage in Denver, Colo.

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A 1930s anti-marijuana movie poster was part of an exhibit at the DEA Museum and Visitors Center in Arlington, Va. After the repeal of alcohol prohibition in 1933, Harry Anslinger, who headed the Federal Bureau of Narcotics, turned his attention to pot. He told of sensational crimes reportedly committed by marijuana addicts. "No one knows, when he places a marijuana cigarette to his lips, whether he will become a philosopher, a joyous reveler in a musical heaven, a mad insensate, a calm philosopher, or a murderer," he wrote in "Marijuana: Assassin of Youth," in 1937.

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After Japanese troops cut off access to Asian fiber supplies during the war, the U.S. Department of Agriculture released the propaganda film "Hemp for Victory" urging farmers to grow hemp and extolling its use in parachutes and rope for the war effort.

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In this 1997 photo, Murphy Brown, portrayed by actress Candice Bergen, smokes a marijuana cigarette to quell nausea induced by the chemotherapy used to treat her breast cancer.

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In 1949 actor Robert Mitchum, center right, and actress Lila Leeds, left, were sentenced to 60 days in jail on charges of conspiracy to possess marijuana cigarettes in Los Angeles.

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In this 1979 photo, police handcuff a suspect during a drug raid in Miami. Police said eight were arrested and marijuana was seized.

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This 1996 photo shows a television ad aired by Republican presidential candidate Bob Dole's campaign that includes footage from a 1992 MTV interview of a laughing President Clinton saying he would inhale marijuana if given the chance to relive his college days. The words on the screen read, ''Clinton's liberal drug policies have failed.''

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