In American history, perhaps the turning point from cannabis as medicine to marijuana as social evil happened rather innocuously with an act by Congress - the marijuana tax stamp act of 1937.
America was in a deep depression. Over-production and financial manipulation. To grow cannabis, you needed a stamp. The Feds were not issuing any stamps.
This was not the first time that hemp as an industrial commodity, and marijuana as medicine, first became stigmatized, despite the cannabis plant’s incredible track record as medicine, food, and textiles.
Yet it did shape harsh political, legal, and social realities for decades.