How did Marijuana Become illegal?

What is hemp? Just another word for marijuana?

Yeah, and that's one of the things that happened in 1937. Cannabis Hemp was one of history's most widely used plants. Tincture of Cannabis was the basis for almost every patent medicine prior to the discovery of aspirin. Hemp was used for rope, twine, and cloth.

Sailing ships were loaded with hemp. The word "canvas" is derived from "cannabis", because that's what canvas was. Sails were made of hemp because salt water deteriorated cotton. Old sails were made into wagon covers and ultimately original Levi's Jeans. And the pressed oil from hemp seeds was used for paints and varnishes.

Everyone knew what hemp was. But nobody knew what marijuana was.