Answer:

1. Rise of racism and targeted propaganda. End of Mexican Revolution resulted in many Mexican immigrants coming into US in 1910, articles in the New York Sun, Boston Daily Globe and other papers decried the "evils of ganjah smoking" and suggested that some immigrants used it "to key themselves up to the point of killing. " Washington v. Sessions, 17-cv-05625 (AKH), Pg. 19, Fn. 87.
2. The Reefer Madness Era and Marijuana Tax Stamp Acts of 1937.
3. 1970 federal Controlled Substances Act – 21 USC 801 et seq
4. Schaeffer Commission recommends removing cannabis from Schedule I
5. JOHN EHRLICHMAN, ESQ – WHITE HOUSE COUNSEL:

"The Nixon campaign in 1968, and the Nixon White House after that, had two enemies: the antiwar left and black people. You understand what I'm saying? We knew we couldn't make it illegal to be either against the war or black, but by getting the public to associate the hippies with marijuana and blacks with heroin. And then criminalizing both heavily, we could disrupt those communities. We could arrest their leaders. raid their homes, break up their meetings, and vilify them night after night on the evening news. Did we know we were lying about the drugs? Of course we did."

[Report] | Legalize It All, by Dan Baum | Harper's Magazine (harpers.org)