The Acid Tests were a series of parties held by author Ken Kesey primarily in the San Francisco Bay Area during the mid-1960s, centered on the use of and advocacy for the psychedelic drug LSD, commonly known as "acid". LSD was not made illegal in California until October 6, 1966.

Augustus Owsley Stanley III was an American-Australian audio engineer and clandestine chemist. He was a key figure in the San Francisco Bay Area hippie movement during the 1960s and played a pivotal role in the decade's counterculture. Under the professional name Bear, he was the sound engineer for the Grateful Dead, recording many of the band's live performances. Stanley also developed the Grateful Dead's Wall of Sound, one of the largest mobile sound reinforcement systems ever constructed. Stanley also helped Robert Thomas design the band's trademark skull logo.