[I]n 1915 Utah became the first state in the Union to criminalize marijuana. The impetus for the ban came from the LDS Church, which was concerned about increasing marijuana use among its members. Latter-day Saints, it turns out, were way ahead of the curve when it came to smoking dope, thanks to the polygamists who’d developed a taste for cannabis in Mexico, where some six thousand of them had fled by the early years of the twentieth century to escape federal prosecution. In the summer of 1912, the Mexican Revolution flared through northern Mexico, and the escalating violence compelled most of the expatriate polygamists to return to Utah, where they introduced marijuana into the broader Mormon culture, alarming the LDS general authorities.
— Jon Krakauer, Under the Banner of Heaven