Considered by pop-culture critics to be the quintessential underground comic book of the 1960s, Zap Comix can trace its genealogy to the publication of Jack Jaxon's God Nose in 1963. By 1999, there were estimated to be more than two million copies of the countercultural Zap Comix in print, including such classics as the sexually explicit "Fritz the Cat" series and the trippy "Mr. Natural" books. Three men, working out of the San Francisco Bay area, were chiefly responsible for the Zap Comix phenomenon: Don Donahue and Charles Plymell were instrumental in securing the money and arranging the distribution of the early issues, while visionary cartoonist Robert Crumb assumed editorial control. Crumb, a Philadelphia native with no formal art training, was to become one of underground comics' most influential creators.

A one-time illustrator for the American Greeting Card Company, Crumb began doing freelance work for Help magazine in...