Why is marijuana illegal?

Who knows. This country is way too uptight about it. It mainly streams from propaganda in the 20's about "reefer madness" and all that BS.
When I was in Athens, Greece this summer with some friends we smoked with some locals on the Acropolis...in public! You could never do something like that here!

This answer is based entirely on hearsay, but well...

So in the early twentieth century, the US put forth an increased effort to regulate drugs and outlaw others, including opiates, marijuana, etc. A wide variety of social factors contributed, but in the case of marijuana, federal lobbies acting on behalf of the cotton industry had a decisive effect. Hemp fiber, which comes from any plant in the cannabis family, is the strongest natural fiber. Also, marijuana isn't called "weed" for no reason: it grows very easily, in almost any climate. In the early twentieth century, therefore, the US had a bunch of slaveless cotton farmers who had been hegemonic due to slave labor but who now faced a competitive threat from people wanting to farm cannabis...which makes stronger and higher-quailty paper, clothing, etc. Luckily, big investors in the cotton industry, including Dupont, had the strength to convince Congress that since certain strains of cannabis (e.g., indica, sativa) qualified as mind-altering substances, well, they should be outlawed along with heroin, etc. And there you go. Big business in the US outlaws a substance way less socially destructive than alcohol. Why? Because of the interests of capital. While capital also spends lots of time keeping bullshit like tobacco...which is much, much more addictive and deadly...legal legal legal.

great answer, i knew it was capitalist fueled

The force of the cotton industry has been part of all the explanations I have read. Another factor, as I understand it, was a wave of anti-immigrant sentiment in the early twentieth century. Sorry for the lack of details, but basically there were several high profile murder cases in different latino neighborhoods where marijuana consumption was somewhat common. Alarmist media and politicians connected such acts with the "crazy weed" and proceeded to use the marijuana issue as a way to criminalize and crack down on immigrant youth.

Since Marijuana has been pushed into the underground or black market, the argument is now commonly made that it is a "gateway drug" to harder drugs and thus should be illegal. Chemically speaking it is no more a gateway drug than cigarettes or alcohol, but may function as such because people who buy marijuana have to go through a dealer (rather than some government regulated source) that oftentimes is a source of hard drugs, and thus users are exposed to or have established access to harder drugs. Also due to its illegal status marijuana has a stigma; once a person has overcome the stigma of trying illicit drugs, there is less of a barrier for trying other illicit drugs that actually pose a substantial risk to one's health and to society.

Historian Martin Booth writes a scholarly history of cannabis called simply "Cannabis: A History." It is interesting and lively exploration of the social, political, cultural, economic and botanical history of the plant.

As a psychotic drug it can cause side effects such as anxiety, panic attacks, paranoia and in rare cases schizophrenia (it doesn't cause it, but can trigger it if you happen to carry the gene i.e. it runs in your family, or make it worse if you already have it). Considering it was already made illegal for the above reasons I suppose recent studies have just reinforced its classification as an illegal substance.

From personal experience I'd say steer clear of the stuff. A lot of people I know who smoked pot heavily over a long course of time became unnaturally anxious about the strangest things - such as not being able be around tall buildings in case someone inside had a sniper rifle.

Here are a few good links: http://nitawriter.wordpress.com/2007/08/07/pot-can-cause-mental-illness-says-the-lancet/
http://www.livescience.com/health/070501_ap_pot_bad.html (I know the link says 'pot bad' which is laughable but it really is a useful article!)

@soethe6 - Good answer man! don't forget how screwed the paper industry would be as well as big corporations that can't patent something like marijuana and therefore can't make gobs of loot on it!

In regards to Marijuana being used by Mexican Immigrants that’s true, however that was only one of the many fronts for the push to ban marijuana from early 30’s to the early 70’s EG: Marijuana makes you kill, Marijuana makes you insane, marijuana was brought in by communists (Russia) campaign. All of these amongst others were used as propaganda by the media to persuade the American public to ban the substance.

ALSO in regards to Marijuana being a “psychotic drug”, The chances of becoming a schizophrenic in general is only 1% casual use of Marijuana is only 2% Heavy use is 6% Your chances are very slim. New clinical studies and efforts by Dr John Marsden push to clear away the FALSE answers we have instilled in our minds about Marijuana.

THE END =D