(History) "For most of American history, growing and using marijuana was legal under both federal law and the laws of the individual states. By the 1840s, marijuana’s therapeutic potential began to be recognized by some U.S. physicians. From 1850 to 1941 cannabis was included in the United States Pharmacopoeia as a recognized medicinal.4 By the end of 1936, however, all 48 states had enacted laws to regulate marijuana.5 Its decline in medicine was hastened by the development of aspirin, morphine, and then other opium-derived drugs, all of which helped to replace marijuana in the treatment of pain and other medical conditions in Western medicine.6"

Source

Eddy, Mark, "Medical Marijuana: Review and Analysis of Federal and State Policies," Congressional Research Service (Washington, DC: March 31, 2009), p. 1.
http://www.fas.org/sgp/crs/mi…