The Acid Tests were a series of parties set up around the San Francisco area in 1965-66 by author Ken Kesey and the Merry Pranksters centred around the use of the psychedelic drug LSD, along with light shows, film projection and improvised music, and were instrumental in the spread of the psychedelic movement across California and the birth of the Grateful Dead. Jerry Garcia explained The Acid Test was the prototype for our whole basic trip... We were lucky to have a little moment in history when LSD was still legal and we could experiment with drugs like we were experimenting with music. It wasn't a gig, it was the Acid Test... Anything was O.K.. It was farout beautiful magic. We had no reputation and nobody was paying to see us or anything like that. We weren't the headliners, the event was. Anything that happened was part of it. There was always the option to not play. ...The freedom is what I loved about it.

The first known use of this poster was for the Acid Test at Muir Beach, 11th December, 1965, printed on the same goldenrod stock with Muir Beach in the tour blank. Only one is known to have survived, originally owned by Ken Kesey. White variants have turned up for the Test at the Big Beat, Palo Alto on 18th December, 1965, and both white and blue variants from the Fillmore Acid Test on 8th January, 1966, the last known use of this design. The poster gives the instructions This grand thing can be made very long & thin by cutting up the middle... so that one half could be placed above the other to paste on telephone poles or streetlights. It is believed that the goldenrod stock were stashed away for some reason, as a few dozen tour blanks on goldenrod are known to have survived.