When was marijuana use first banned and why?

Marijuana use was first banned in the United States in 1937 with the passage of the Marihuana Tax Act. The Act placed strict regulations on the sale, possession, and use of marijuana, and effectively made marijuana illegal in the US. The Act was passed despite little scientific evidence of marijuana's negative effects, and was largely driven by anti-Mexican sentiment and misinformation about the drug.

The Act was heavily influenced by the Federal Bureau of Narcotics, led by Harry Anslinger, who campaigned against marijuana by spreading misinformation and racist stereotypes about Mexican immigrants and African Americans, who were said to be the main users of marijuana at the time. He claimed that marijuana use led to violence, insanity and moral decay, and that it was a major threat to society.

The Act's passage marked the beginning of marijuana prohibition in the United States, and similar laws were soon passed in other countries. It was not until the 1970's that the laws regarding marijuana began to be reformed, and today several states have legalized marijuana for medical or recreational use.