1. "Marijuana" is a Mexican term that originally was applied to low-quality tobacco.

2. The plant was cultivated in China for therapy (and recreation) over 4,700 years ago.

3. More than 20 prescription medicines containing marijuana were sold in U.S. pharmacies at the turn of the 20th century. Pot-based medications were commonly available until 1942, when cannabis was stricken from the U.S. Pharmacopeia, the official compendium of drugs considered effective. From 1937 to 1942 the federal government collected a tax of $1 per ounce for such drugs.

4. More than 20,000 studies on marijuana and its components have been published, according to the National Organization for the Reform of Marijuana Laws, an advocacy group. Of these, around 100 have looked into therapeutic value on human subjects.