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 entirely on the use of, and advocacy of, the psychedelic drugLSD, also known as "acid". LSD was not made illegal in California until October 6, 1966.
27 November; Soquel, California -- The very first Acid Test was a party at Ken Babbs' house on 27th November 1965, although Ken Babbs recalls it as Halloween night. A flyer of the Warlocks, however, (one week before the band became known as the Grateful Dead) shows they played at Soquel as the Warlocks on November 27. There is no evidence this flyer is genuine, and several witnesses confirm that the Warlocks / Grateful Dead did not play at Soquel, but that they did mess around with Prankster instruments. In his book, Phil Lesh confirms that he attended: 'We were at the first Test not to play, but just to feel it out, and we hadn't brought any instruments or gear'  Most likely Phil Lesh, Bob Weir and Jerry Garcia, members of the future Grateful Dead did attend this party.
4 December; San Jose, California (first performance by the Grateful Dead, until then known as the Warlocks)
16 March; Houston, Texas (Brown College, Rice University) (despite the "graduation" concept of the final West Coast Acid Test, the actual final Acid Test of The Merry Pranksters was organized in Texas by Kesey's friend Larry McMurtry)
24 October; Congress passes the Staggers-Dodd Bill, criminalizing the recreational use of LSD-25
Ramon Sender co-produced the Trips Festival with Ken Kesey and Stewart Brand. It was a three-day event that, in conjunction with The Merry Pranksters, brought together the nascent hippie movement for the first time. The Trips Festival was held at the Longshoreman's Hall in San Francisco in January 1966. Counterculture sound engineer Ken Babbs is mostly credited for the sound systems he created for the Trips Festival. Prior to Babbs' creation, it was discovered that particular music usually sounded distorted when cranked to high levels because of the cement floor on the San Francisco Longshoreman's Union Hall (where the Trips Festival was taking place). Babbs being a sound engineer resolved the problem. He made sound amplifiers that would not create distorted sounds when turned up to high sound levels.