The Spectrum posted an op/ed piece as a follow up to Barney Frank's proposed end to Marijuana prohibition for adults in the US. It's a good read and gives a brief overview of how Marijuana became illegal:

Massachusetts Rep. Barney Frank is proposing a bill that would remove federal penalties for possession and use of small amounts of marijuana.

Why do we need a federal bill?

Because the rest of the country is far behind Alaska, California, Colorado, Maine, Minnesota, Mississippi, Nebraska, Nevada, New York, North Carolina, Ohio and Oregon in decriminalizing the herb, with Michigan on the verge of approving a similar bill. We need a federal bill because we need to put an end to this fruitless, expensive prohibition once and for all.

Is legalizing Marijuana a reachable goal for the near future?