One popular account:
And then there's a passage from David Nutt’s Drugs Without the Hot Air:
In the USA, cannabis was strongly associated with immigrants from Mexico, and even the spelling was altered from "marihuana" to "marijuana" (to rhyme with Tijuana) to make it seem more Mexican. Among the most vocal part of the press spreading rumours about its negative effects were the outlets owned by William Randolph Hearst, a media tycoon who had invested heavily in the wood pulp industry. Since hemp paper posed direct competition to wood pulp paper, he had an economic stake in limiting hemp production, and recognised that if controls were placed on cannabis because of its psychoactive effects, it would become more difficult to grow the plant for other purposes.
Reihan has doubts about this narrative:
I can’t speak to the soundness of Nutt’s account of Hearst’s central role. It sounds like one of those stories reform advocates would very much like to be true.