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If you look for the roots of America’s ban on cannabis, you’ll find nearly all roads lead to a man named Harry Anslinger. He was the first commissioner of the Federal Bureau of Narcotics, which laid the ground work for the modern-day DEA, and the first architect of the war on drugs.

Anslinger was appointed in 1930, just as the prohibition of alcohol was beginning to crumble (it was finally repealed in 1933), and remained in power for 32 years. Early on, he was on record essentially saying cannabis use was no big deal. He called the idea that it made people mad or violent an “absurd fallacy.”

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But when Anslinger was put in charge of the FBN, he changed his position entirely.

Harry J. Anslinger, commissioner of the Treasury Department’s Federal Bureau of Narcotics, poses for a photo on September 24, 1930. AP

“From the moment he took charge of the bureau, Harry was aware of the weakness of his new position. A war on narcotics alone — cocaine and heroin, outlawed in 1914 — wasn’t enough,” author Johann Hari wrote in his book, “Chasing the Scream: The First and Last Days of the War on Drugs.” “They were used only by a tiny minority, and you couldn’t keep an entire department alive on such small crumbs. He needed more.”

Consequently, Anslinger made it his mission to rid the U.S. of all drugs — including cannabis. His influence played a major role in the introduction and passage of the Marijuana Tax Act of 1937, which outlawed possessing or selling pot.

Fueled by a handful of 1920s newspaper stories about crazed or violent episodes after marijuana use, Anslinger first claimed that the drug could cause psychosis and eventually insanity. In a radio address, he stated young people are “slaves to this narcotic, continuing addiction until they deteriorate mentally, become insane, turn to violent crime and murder.”

In particular, he latched on to the story of a young man named Victor Licata, who had hacked his family to death with an ax, supposedly while high on cannabis. It was discovered many years later, however, that Licata had a history of mental illness in his family, and there was no proof he ever used the drug.

The problem was, there was little scientific evidence that supported Anslinger’s claims. He contacted 30 scientists, according to Hari, and 29 told him cannabis was not a dangerous drug. But it was the theory of the single expert who agreed with him that he presented to the public — cannabis was an evil that should be banned — and the press ran with this sensationalized version.

Narcotics Commissioner Harry J. Anslinger announces a series of raids in the nation’s big cities aimed at crippling the narcotics traffic in New York on Jan. 4, 1958. More than 500 suspected peddlers were bagged. AP

The second component to Anslinger’s strategy was racial. He claimed that black people and Latinos were the primary users of marijuana, and it made them forget their place in the fabric of American society. He even went so far as to argue that jazz musicians were creating “Satanic” music all thanks to the influence of pot. This obsession eventually led to a sort of witch hunt against the legendary singer Billie Holiday, who struggled with heroin addiction; she lost her license to perform in New York cabarets and continued to be dogged by law enforcement until her death.

“The insanity of the racism is a thing to behold when you go into his archives,” Hari told CBS News. “He claims that cannabis promotes interracial mixing, interracial relationships.”

The word “marijuana” itself was part of this approach. What was commonly known as cannabis until the early 1900s was instead called marihuana, a Spanish word more likely to be associated with Mexicans.

“He was able to do this because he was tapping into very deep anxieties in the culture that were not to do with drugs — and attaching them to this drug,” Hari said. Essentially, in 1930s America, it wasn’t hard to use racist rhetoric to associate the supposed harms of cannabis with minorities and immigrants.

So as the nationwide attitude towards cannabis began to fall in line with Anslinger’s, he testified before Congress in hearings for the Marijuana Tax Act. His testimony centered around the ideas he had been pushing all along — including a provocative letter from a local newspaper editor in Colorado, saying “I wish I could show you what a small marihuana cigaret can do to one of our degenerate Spanish-speaking residents.”

All these years later, many of the threads in Anslinger’s arguments are still present in the American conversation about legalizing marijuana. The act was passed in 1937, and the rest, they say, is history.