Rock ’n’ roll took a mind-bending turn 50 years ago at an unassuming 19th-century Victorian house on a San Jose lot that’s now home to City Hall.

It was there, on Dec. 4, 1965, that the Grateful Dead was officially born.

Yes, San Jose. The legendary band forever associated with San Francisco had already been gigging in the South Bay and Peninsula as The Warlocks and before that as a Palo Alto-based outfit known as Mother McCree’s Uptown Jug Champions. But it wasn’t just the new name that made the Dec. 4 concert so significant. It was also its role in the first real public “Acid Test,” a series of parties built around the collective use of the psychedelic drug LSD, hosted by “One Flew Over the Cuckoo’s Nest” author Ken Kesey and his network of friends, artists, writers and musicians called the Merry Pranksters.

A watershed moment

The melding of rock and LSD at these parties/social experiments, considered a watershed moment in the birth of the hippie movement, had a huge impact on the Dead, shaping its psychedelic rock sound and, perhaps more important, its foundation for the communal concert experience and the close-knit collective of fans it created.

“It was an overwhelming and absolute influence,” says Dennis McNally, biographer and former publicist for the band, which played more than 2,300 concerts. “It was the template for how they related to their audience for the next 30 years.”

The musicians — Jerry Garcia, Bob Weir, Bill Kreutzmann, Ron “Pigpen” McKernan and Phil Lesh — had played their first gig as The Warlocks at a pizza parlor in Menlo Park on May 5 of that year. But soon after, Lesh discovered while browsing a record store that there was at least one other band going by that name. Interestingly, another heavily influential band, The Velvet Underground, also got its start as The Warlocks.

Around the same time, Garcia and crew met up with Kesey, who was also living on the Peninsula, and the band began playing at his Acid Tests. They were still going by The Warlocks at the first Acid Test, a comparatively small, private gathering held on Nov. 27, 1965, at a home in Soquel. They changed to the Grateful Dead in time for the first big, public (and second overall) Acid Test, held in a home just down the street from San Jose Civic Auditorium, where the Rolling Stones had performed earlier in the evening. And while it’s rumored that members of the Stones were at the Acid Test, that’s still the subject of debate.

Lesh recalled that he knew that night the band was on to something.

“The chaos at the San Jose Test didn’t stop us from playing as long and as loud as we could, and we found that while high we were able to go very far out musically but still come back to some kind of recognizable space or song structure,” Lesh writes in “Searching for the Sound: My Life With the Grateful Dead.” “I knew instantly that this combination — acid and music — was the tool I’d been looking for.”

“The Acid Tests offered an entirely new approach to the kind of music they wanted to play,” says Nicholas Meriwether, archivist at the Grateful Dead Archive at UC Santa Cruz. “They wanted to play in an environment that didn’t have rigid structure. They wanted to play in an environment in which the boundaries between the performer and audience were either nonexistent or awfully permeable.”

If the Dec. 4 show was a watershed moment in Bay Area music history, it has not been publicly treated that way. The 1895 Victorian that housed the event was relocated by the San Jose Redevelopment Agency to make way for City Hall. And there is no marker or plaque at City Hall or in its vicinity that celebrates the location as the birthplace of the Grateful Dead.

At least not yet. A group of residents has asked the city to place a plaque or marker recognizing the site of the first Grateful Dead show. Dan Orloff, one of the principals leading the charge, says the designation would honor “one of the great moments of pop music history” and help correct the popular misconception that San Francisco has the market cornered on local music history.

“It’s more evidence that this entire Bay Area really contributed to an irreplaceable catalog of popular music,” says Orloff, owner of the marketing firm Orloff Williams and founder of musical history organization Bay Area Rocks.

Lynne Brown, a member of the San Jose Arts Commission who has been assisting with the plaque effort, says the ultimate decision rests with the City Council, which has no timetable to act on the matter.

A new gig

As for the Dead, the long strange trip isn’t over just yet. Surviving members of the band — Mickey Hart, Bill Kreutzmann and Bob Weir — are teaming with pop-rock guitarist John Mayer in an outfit called Dead and Company, and are scheduled to play Dec. 27-28 at the Bill Graham Civic Auditorium in San Francisco. The stand follows the massive “Fare Thee Well: Celebrating 50 Years of Grateful Dead” concerts which drew hundreds of thousands of fans to Soldier Field in Chicago and Levi’s Stadium in Santa Clara over the summer.

The 50th anniversary celebration of the First Acid Test

Featuring: Slugs N Roses, Ken Babbs, dedication of historic marker of First Acid Test

When: Friday, Dec. 4, 8 p.m.

Where: Don Quixote’s International Music Hall, 6275 Hwy. 9, Felton

Tickets: $12 advance; $15 at the door

Details: www.donquixotesmusic.info

Note: Lee Quarnstrom, original Merry Prankster, will be on hand at Bookshop Santa Cruz Thursday, Dec. 3 at 7 p.m. in a free event to commemorate the 50th anniversary of the First Acid Test.