Some films from the 1930s have entered the public domain and are available on youtube.
As one Youtube comment writer puts it, " Our grandparents smoked pot!"
(That's only part I of the film, more parts here.)
From wikipedia: "Reefer Madness is a 1936 propaganda film revolving around the tragic events that follow when high school students are lured by pushers to try "marihuana": a hit and run accident, manslaughter, suicide, rape, and descent into madness all ensue. The film was directed by Louis J. Gasnier and starred a cast composed of mostly unknown bit actors. It was originally financed by a church group and made under the title Tell Your Children."
Complete wikipedia article.
