January 16, 1919: The 18th Amendment (alcohol prohibition) is declared ratified and is scheduled to take effect in one year.

January 16, 1920: At midnight, the 18th Amendment becomes law, making alcohol illegal.

January 21, 1943: The New York Times reports that swing-band leader Gene Krupa pleaded innocent to a charge that he contributed to the delinquency of a minor by asking 17-year-old John Pateakos to fetch marijuana cigarettes from his hotel room for him.

January 16, 1980: Paul McCartney is arrested by Japanese customs officials at Tokyo International Airport when they find two plastic bags in his suitcases containing 219 grams of marijuana (approximately 7.7 ounces). Concerned that McCartney would be refused a US visa under immigration laws if convicted and be unable to perform in an upcoming Wings concert in the US, Sen. Edward Kennedy calls first secretary of the British Embassy D.W.F. Warren-Knott on January 19. McCartney is released and deported on January 25.

January 18, 1990: Mayor Marion Barry of Washington, DC, is arrested after hidden cameras record him smoking crack cocaine with ex-girlfriend Hazel Diane "Rasheeda" Moore in her room at the Vista Hotel.

January 22, 1992: The California Research Advisory Panel concludes that drug prohibition has a more harmful effect on society and the individual than illegal drugs.

January 20, 1997: The Lymphoma Foundation calls for rescheduling of marijuana as a medicine and the reopening of the Investigational New Drug compassionate access program.

January 19, 1999: Twenty heavily armed officers from the Placer County sheriff's department in northern California raid the home of Steve and Michele Kubby.

January 20, 2000: John Warnecke, former friend and colleague of Al Gore at The Tennessean, contradicts Gore's characterization of his past marijuana use as minimal. He notes that Al Gore was a regular user, and that he used marijuana for at least four years after he claims to have stopped.

January 21, 2003: Ed Rosenthal's federal trial for marijuana cultivation begins. Rosenthal was growing medically with authorization from the city of Oakland, California, but his legal team is barred by Judge Charles Breyer from informing the jury of this. Rosenthal is ultimately convicted but sentenced to one day, time already served.

January 21, 2003: A Sydney Morning Herald (Australia) article discusses a Commonwealth Government report that found tobacco and alcohol accounts for 83 percent of the cost of drug abuse in Australia, dwarfing the financial impact of illegal drugs.

January 21, 2003: MAPS and California NORML sign a contract for a $25,000 protocol study to evaluate the contents of the vapor stream from the Volcano Vaporizer.