Marijuana was made illegal for economic reasons (because corporations involved with lumber, cotton, and other things didn't want the competition hemp provided), and for reasons of social control (control of minorities, and later student activists, who dared to challenge the establishment). The government just used the "dangerous" label as an excuse to get the law accepted -- and a lot of the population bought into that lie (and many still do).
It is time to recognize the truth, and legalize the growth, possession, and use of marijuana.