How about from the Federal Bureau of Investigation, Uniform Crime Reports for the United States 2000 (Washington DC: US Government Printing Office, 2001), pp. 215-216, which shows:
Although people may think that the Drug War targets drug smugglers and 'King Pins,' in 2000, 46.5 percent of the 1,579,566 total arrests for drug abuse violations were for marijuana -- a total of 734,497. Of those, 646,042 people were arrested for marijuana possession alone. This is an increase over 1999, when a total of 704,812 Americans were arrested for marijuana offenses, of which 620,541 were for possession alone.
That's all well and good. You may have missed the point. When has ANYONE been imprisoned for smoking pot?