These documentaries tell what made cannabis and hemp illegal.

Cannabis and Hemp are two very different strains on cannabis plant. Marijuana was a mexican tobacco that made people crazy. Mexicans were a problem then. A prohibionist Harry J. Anslinger wanted to make cannabis look bad so he started to call cannabis as marijuana to connect it to the mexican crazy tobacco.

This picture shows why hemp was also criminalized.

Hemp is so versatile, easy and cheap to produce that other industries can't compete with it. That's why it was also made illegal with cannabis. Hemp can't get you high, it doesn't have THC in it.

This is the biggest reason why cannabis was made illegal. Pharmaceutical industry can't sell you extremely expensive drugs when you can treat yourself with cannabis.