Cannabis as a whole (including all forms of the plant) was outlawed in 29 states by 1931 due to the Prohibition era’s view of all intoxicants. Shortly after, the Marijuana Tax Act of 1937 imposed an excise sales tax on the sale, possession or transfer of all hemp products, which effectively criminalized all but industrial uses for the plant. Industrial hemp was grown and sold in the U.S. until the end of WWII and the last legal hemp fields were planted in 1957 in Wisconsin. In 1970, Richard Nixon signed the Controlled Substances Act of 1970, repealing the Marijuana Tax Act and listing Marijuana as a Schedule 1 drug – along with LSD, heroin and ecstasy. It was labeled as having zero medicinal properties.
Many years down the road, California passed the Compassionate Use Act of 1996, which legalized the plant in California for medicinal purposes. Colorado and Washington were the first to fully legalize the plant for recreational use and many states have followed in their footsteps.