This rarely seen original 1967 poster was made for a Big Brother & The Holding Company run of shows at the Ark in Sausalito with Moby Grape in support. During the heyday of psychedelic rock, Sausalito became a hangout for many of the Bay Area bands. After they finished their main gigs in San Francisco, they would hop across the Golden Gate bridge and play late night sets at The Ark. The venue was a favorite destination for these shows as it was the only venue open late. The Ark was only open for a short time but many of the SF bands played there including Steve Miller and Santana.
As the artist's design credit does not appear on this poster it fell into the category of "public domain" when it came to copyright protection, and therefore it could be reprinted without permission (that was the law in 1967), which is exactly what Portal Publications did to many of The Ark posters (including this one). Therefore, the Portal printing credit on one of these posters earmarks it as a reprint, not an original first printing like this one.