I think in order to understand the current attitudes towards marijuana and cannabis, it helps to know a little of the history of the use of Cannabis in the US (and in the Colonies).
As early as 1619, King James I decreed that the Virginia Company require each colonist to grow 100 cannabis plants for the specific purpose of export for fiber. During the 18th and 19th centuries hemp became a widely cultivated crop for industrial use. In 1839, William Brooke O’Shaughnessy (an Irishman, by the way, @NerdyKeith) who had worked and studied extensively in India, introduced its use to Western Medicine.
During the 19th century, use of cannabis in patent medicines, as well as recreational use spread to virtually every state and area in the US. Hashish parlors competed with opium dens for recreational customers. In the 1850’s, marijuana was listed as a fashionable narcotic in an article in the New York Times.
Around that time laws started to spring up regulating the use of certain drugs and requiring that they be sold only through pharmacies. These laws were generally aimed at opiates, but many included hemp-based drugs in the regulations.
The Pure Food and Drug Act was then passed by the United States Congress in 1906 and required that certain special drugs, including cannabis, be accurately labeled with contents. This was in response to the great wave of Patent Medicines. The vilification of the herb continued on up into the 1930’s, when the Federal Bureau of Narcotics published this flyer, and Reefer Madness.
In 1970 Cannabis was listed as a Schedule I drug as defined by the US Controlled Substances Act.