Well right now I'm very fascinated with 1920s Berlin. I mean probably the more interesting thing would be to go to the beginning of civilization or precivilization - like polytheistic times. It would be interesting to see what came before modern religion and culture - what circumstances created the environment or the need for it.
Who most benefits from keeping marijuana illegal? The greatest beneficiaries are the major criminal organizations in Mexico and elsewhere that earn billions of dollars annually from this illicit trade - and who would rapidly lose their competitive advantage if marijuana were a legal commodity.