Drug use has increased in all categories since the beginning of prohibition on January 17, 1920, with the exception of opium; its use is at a fraction of its peak level. A major decline in the use of opium started after the Harrison Act of 1914 was initiated. Use of heroin peaked between 1969 and 1971, marijuana between 1978 and 1979, and cocaine between 1987 and 1989.
Between 1972 and 1988, the use of cocaine increased more than fivefold. The usage patterns of the current two most culturally popular drugs: amphetamines and ecstasy, have shown similar gains.
Secretly, many senior officials of the Reagan administration illegally trained and armed the NicaraguanContras, who were funded by the shipment of large quantities of cocaine into the United States using U.S. government aircraft and U.S. military facilities. Funding for the Contras was also obtained through the illegal sale of weaponry to Iran. When this practice was discovered and condemned in the media, it was referred to as the Iran–Contra affair.
In 1996, California voters passed Proposition 215, legalizing the growing and use of marijuana for medical purposes. This created significant legal and enforcement conflict between federal and state government laws. Courts have since decided that a state law in conflict with a federal law concerning cannabis is not valid. Cannabis is restricted by federal law (see Gonzales v. Raich). In 2010 California Proposition 19 (also known as the Regulate, Control & Tax Cannabis Act) was defeated with 53.5% 'No' votes, and 46.5% 'Yes' votes.