Nor for the 5000 years before that that the plant was used for medicine.
But let's be clear, it was industrial hemp that got the laws changed. They used the "it will make black men rape white women" thing just to scare the folks. Like most things in Congress, it was about the money. What got the ball rolling was the invention of a machine that would separate the parts of the hemp stem. Up until then, it had been done by hand. Long and expensive.
Hemp production was neck and neck with cotton after the Civil War. Prohibition was rushed through Congress because three men had lots of money at stake. Du Pont produced the chemical to make paper out of wood, {until then, most quality paper was made from hemp, but cheaper, newsprint was made from wood. The new machine was going to lower the price of hemp paper}. Mellon was his banker, and had invested heavily into the newest Du Pont product, nylon, which was trying to get a toehold in the cordage industry {which was dominated by hemp}. Hearst had bought up millions of acres of tree land {which would fall in value if wood didn't increase it's market share of the paper industry}. So each man had millions of reasons to turn the county against hemp. But it was a common farm product, so they had to come up with something to change popular opinion. Hearst just happend to own a newspaper, so he ran made up stories about blacks and Mexicans raping white women after smoking "Marihuana." Which was a word Americans had never heard. It sounded Mexican, thus scary. We had always called it cannabis, so most people didn't even know it was the plant they had known all their lives.
The rest is history. Billions of dollars spent, thousands of people killed and imprisoned. But the Du Pont, Mellon and Hearst families are doing fine.