Cannabis is mainly illegal because of these guys.
When powerful businesses don’t like something, they can usually get something done about it. The 1937 criminalization of marijuana is a case where this manipulation is obvious, according to Herer. Hemp threatens certain powerful businesses today, just as it did in 1937.
As the methods for processing hemp into paper and plastics were becoming more readily available and affordable, business leaders including William Randolph Hearst and DuPont stood to lose fortunes. They did everything in their power to have it outlawed. Luckily for Hearst, he was the owner of a chain of newspapers. DuPont’s chief financial backer Andrew Mellon (also the Secretary of the Treasury during President Hoover) was responsible for appointing Harry J. Anslinger, in 1931 as the head of the Federal Bureau of Narcotics and Dangerous Drugs.
Hearst’s papers deplorably published enhanced accounts of marijuana-crazed black men raping white women. With these sensationalist newspaper stories as his support, Anslinger testified before Congress that, “Marijuana is the most violence causing drug in the history of mankind.”
Anslinger completely contradicted himself later--before Congress again in 1948—when he testified that marijuana caused its users to become peaceful and pacifist, and that Communists would use marijuana to weaken America’s will to fight.
So the main reason why it's illegal can be tied into racism, Anslinger was quoted saying "Reefer makes the darkies think they're better than white men." And since this was back when racism was at it's peak pretty much anyone would listen to a white man preach about anything against african americans.
A very interesting piece of that history is that only two days before the 1937 marijuana hearings, the American Medical Association (AMA) had just realized that the plant that Congress intended to outlaw was known medically as cannabis, which from 1850 to 1937 had been recorded as being