The historical importance of this book transcends the underground comix movement. In many ways, this book had a significant influence on the way the entire comic book industry would be forced to reexamine itself in the area of censorship (comics code), paving the way towards better acknowledging artistic merit, autonomy and rightful ownership of published works - an influence that is still evident in today's alternative and independent comics movement.
Zap Comix #1 is most widely recognized for catapulting comic creator Robert Crumb's success, and to say it inspired an entire generation of artists would be an understatement.
First Print copies of Zap Comix 1 are distinguished by a 25¢ cover price, and the words "Printed by Charles Plymell" on the lower left corner of the rear cover.
According to the underground comix price guide (1982), first print copies of Zap Comix 1 had an original print run of 5,000. Later writings by the printer Charles Plymell explained how the print numbers were effected by losses in printing and assembly quality (hand-cranked Multilith printer, manual assembly of covers/interiors, trimming and stapling), and that he estimated the count to be closer to 1,500. His wife Pam felt it was much lower - maybe even as low as 600 copies.
This doesn't take into account that this comic was produced at a time when sentiment of anti-establishment and indifference towards authority was at an all-time high - a movement met by vigilant confiscation of works considered "political propaganda," forcing first print Zap Comix 1's distribution to occur out of a baby stroller in the Haight-Ashbury district (a predominantly "Hippie" area of San Francisco).
We also know that about 500 copies were burned in a 1970 fire which occurred at Mowry's Opera Theatre.
If there is any indication on the rarity of this book, the census numbers themselves speak volumes, reporting that 46 copies have been graded in 10+ years that CGC has been in business - only 4 copies have graded higher than this copy.