Most of the history of marijuana's criminalization has been based on lies. The actual reasons why marijuana is illegal are:

Racism
Fear
Protection of Corporate Profits
Yellow Journalism
Ignorant, Incompetent, and/or Corrupt Legislators
Personal Career Advancement and Greed

For most of human history, marijuana has been completely legal. It's not a recently discovered plant, nor is it a long-standing law. Marijuana has been illegal for less than 1% of the time that it's been in use. Its known uses go back further than 7,000 B.C. and it was legal as recently as when Ronald Reagan was a boy.

The marijuana (hemp) plant, of course, has an incredible number of uses. The earliest known woven fabric was apparently of hemp, and over the centuries the plant was used for food, incense, cloth, rope, and much more. This adds to some of the confusion over its introduction in the United States, as the plant was well known from the early 1600's, but did not reach public awareness as a recreational drug until the early 1900's.

America's first marijuana law was enacted at Jamestown Colony, Virginia in 1619. It was a law "ordering" all farmers to grow Indian hempseed. There were several other "must grow" laws over the next 200 years (you could be jailed for not growing hemp during times of shortage in Virginia between 1763 and 1767), and during most of that time, hemp was legal tender (you could even pay your taxes with hemp -- try that today!) Hemp was such a critical crop for a number of purposes (including essential war requirements - rope, etc.) that the government went out of its way to encourage growth.

The United States Census of 1850 counted 8,327 hemp "plantations" (minimum 2,000-acre farm) growing cannabis hemp for cloth, canvas and even the cordage used for baling cotton.

The Mexican Connection

In the early 1900s, the western states developed significant tensions regarding the influx of Mexican-Americans. The revolution in Mexico in 1910 spilled over the border, with General Pershing's army clashing with bandit Pancho Villa. Later in that decade, bad feelings developed between the small farmer and the large farms that used cheaper Mexican labor. Then, the depression came and increased tensions, as jobs and welfare resources became scarce.

One of the "differences" seized upon during this time was the fact that many Mexicans smoked marijuana and had brought the plant with them.

However, the first state law outlawing marijuana did so not because of Mexicans using the drug. Oddly enough, it was because of Mormons using it. Mormons who traveled to Mexico in 1910 came back to Salt Lake City with marijuana. The church was not pleased and ruled against use of the drug. Since the state of Utah automatically enshrined church doctrine into law, the first state marijuana prohibition was established in 1915. (Today, Senator Orrin Hatch serves as the prohibition arm of this heavily church-influenced state.)

Other states quickly followed suit with marijuana prohibition laws, including Wyoming (1915), Texas (1919), Iowa (1923), Nevada (1923), Oregon (1923), Washington (1923), Arkansas (1923), and Nebraska (1927). These laws tended to be specifically targeted against the Mexican-American population.

When Montana outlawed marijuana in 1927, the Butte Montana Standard reported a legislator's comment: "When some beet field peon takes a few traces of this stuff... he thinks he has just been elected president of Mexico, so he starts out to execute all his political enemies." In Texas, a senator said on the floor of the Senate: "All Mexicans are crazy, and this stuff [marijuana] is what makes them crazy."

Jazz and Assassins

In the eastern states, the "problem" was attributed to a combination of Latin Americans and black jazz musicians. Marijuana and jazz traveled from New Orleans to Chicago, and then to Harlem, where marijuana became an indispensable part of the music scene, even entering the language of the black hits of the time (Louis Armstrong's "Muggles", Cab Calloway's "That Funny Reefer Man", Fats Waller's "Viper's Drag").

Again, racism was part of the charge against marijuana, as newspapers in 1934 editorialized: "Marihuana influences Negroes to look at white people in the eye, step on white men's shadows and look at a white woman twice."

Two other fear-tactic rumors started to spread: one, that Mexicans, Blacks and other foreigners were snaring white children with marijuana; and two, the story of the "assassins." Early stories of Marco Polo had told of "hasheesh-eaters" or hashashin, from which derived the term "assassin." In the original stories, these professional killers were given large doses of hashish and brought to the ruler's garden (to give them a glimpse of the paradise that awaited them upon successful completion of their mission). Then, after the effects of the drug disappeared, the assassin would fulfill his ruler's wishes with cool, calculating loyalty.

By the 1930s, the story had changed. Dr. A. E. Fossier wrote in the 1931 New Orleans Medical and Surgical Journal: "Under the influence of hashish those fanatics would madly rush at their enemies, and ruthlessly massacre every one within their grasp." Within a very short time, marijuana started being linked to violent behavior.

Alcohol Prohibition and Federal Approaches to Drug Prohibition

During this time, the United States was also dealing with alcohol prohibition, which lasted from 1919 to 1933. Alcohol prohibition was extremely visible and debated at all levels, while drug laws were passed without the general public's knowledge. National alcohol prohibition happened through the mechanism of an amendment to the constitution.

Earlier (1914), the Harrison Act was passed, which provided federal tax penalties for opiates and cocaine.

The federal approach is important. It was considered at the time that the federal government did not have the constitutional power to outlaw alcohol or drugs. It is because of this that alcohol prohibition required a constitutional amendment.

At that time in our country's history, the judiciary regularly placed the tenth amendment in the path of congressional regulation of "local" affairs, and direct regulation of medical practice was considered beyond congressional power under the commerce clause (since then, both provisions have been weakened so far as to have almost no meaning).

Since drugs could not be outlawed at the federal level, the decision was made to use federal taxes as a way around the restriction. In the Harrison Act, legal uses of opiates and cocaine were taxed (supposedly as a revenue need by the federal government, which is the only way it would hold up in the courts), and those who didn't follow the law found themselves in trouble with the treasury department.

In 1930, a new division in the Treasury Department was established -- the Federal Bureau of Narcotics -- and Harry J. Anslinger was named director. This, if anything, marked the beginning of the all-out war against marijuana.