One of the most fun (not necessarily most accurate, but definitely most fun) sources for this is Mezz Mezzrow's autobiography Really the Blues, first published in 1946.

He was a clarinetist who played with Louis Armstrong and Sidney Bechet, and claims to have invented the term "jam session" to describe an informal musical get-together.

He also served time for selling tea, pot, grass... what he called muggles (don't tell JK Rowling). To the point where (he claims) his name, "Mezz," also joined that list of synonyms. "The Johnny Appleseed of Weed", Albert Goldman's cover blurb calls him. He tried taking a bunch of joints into the 1940 World's Fair and the ofay nabbed him.

He also got hooked on opium, and has a fair amount to say about that, as well as a nice little speech to the sentencing judge about the unfairness of drug criminalization.

The book was never a best-seller, but gained a real cult cachet, especially in the 1960s.

Anyway, to start to answer your question, "prevalent" is a little subjective, but in some social strata, it was a lot more common than the dominant culture would really let on, maaan.