The removal of cannabis became effective on November 1, 1942.

Cannabis 1942
Here is a copy of page lxxxvi, (pg. 86), of the 1942 United States Pharmacopoeia USP XII showing that cannabis has been officially removed. This removal of cannabis became effective on November 1, 1942. It is remarkable that several of the drugs kicked out of the 1942 edition of the USP have made their way back into the 2007 edition. Bismuth subgallate is currently on page 1536 and Valarian is on pages 988-990 of the USP 30-NF 25. While a drug may have been removed from the USP it would usually be picked up by the NF or Nationaly Formulary. With respect to cannabis it was not picked up by the NF.