WikiAnswers - Why is marijuana illegal:
"Natural hemp industrialization would have ruined over 80% of Dupont's business.
Andrew Mellon became Hoover's Secretary of the Treasury and Dupont's primary investor. He appointed his future nephew-in-law, Harry J. Anslinger, to head the Federal Bureau of Narcotics and Dangerous Drugs.
Secret meetings were held by these financial tycoons. Hemp was declared dangerous and a threat to their billion dollar enterprises. For their dynasties to remain intact, hemp had to go. These men took an obscure Mexican slang word: 'marihuana' and pushed it into the consciousness of America."