Fifty years ago this summer, more than 100,000 young artists, musicians, activists, bohemians, and dreamers descended on San Francisco's Haight-Ashbury neighborhood.

Bob Schnepf, "Summer of Love/City of San Francisco," 1967. Color offset lithograph poster. Fine Arts Museums of San Francisco, Gift of the Gary Westford Collection, in Honor of Bob (Raf) Schnepf, 2017.7.11. © Bob Schnepf | (Courtesy of the Fine Arts Museums of San Francisco)

While many other cities around the country were dealing with serious racial upheaval, San Francisco was incubating a new social paradigm of alternative living. Participants rejected the Vietnam War, inequality, and material values, and embraced free love, psychedelics, and rock 'n' roll. The social phenomenon was billed as the Summer of Love.

A half-century later, San Francisco's de Young museum is offering a throwback exhibition, The Summer of Love Experience: Art, Fashion, and Rock & Roll, on view through Aug. 20.

The immersive show attempts to honor the trippy mood of the time by mixing music and interactive light shows with the summer's costumes, ephemera, film, photography, fashion, and, perhaps most notably, the vibrant posters that directed people to shows at the Fillmore Auditorium, Avalon Ballroom, and other iconic Bay Area venues.

Bonnie MacLean, "Yardbirds, The Doors, James Colton Blues Band, Richie Havens, July 25-30, Fillmore Auditorium," 1967. Color offset lithograph poster. Fine Arts Museums of San Francisco, Museum purchase, Achenbach Foundation for Graphic Arts Endowment Fund, 1972.53.103. © Bill Graham / Bonnie MacLean | (Courtesy of the Fine Arts Museums of San Francisco)

"It seems surprising, but I don't think the posters in the aggregate have ever really been considered as a visual expression of the San Francisco counterculture's larger ideologies," says Colleen Terry, assistant curator for the Achenbach Foundation for Graphic Arts at the Fine Arts Museums of San Francisco.

"In many ways, the posters can be thought of as surrogates for the dance concerts that brought members of San Francisco's counterculture together," Terry says.

"Even if you couldn't be at the Fillmore, the Avalon, or one of the smaller music venues around town, consuming the posters could go a long way towards identifying with the counterculture."

Stanley Mouse, "'Libertie,' Blood, Sweat and Tears, John Handy, Son House, March 15–17, Avalon Ballroom," 1968. Color offset lithograph poster. Fine Arts Museums of San Francisco, Museum purchase, Achenbach Foundation for Graphic Arts Endowment Fund, 1974.13.151. Artwork by Stanley Mouse. © 1966, 1984, 1994 Rhino Entertainment Company. Used with permission. All rights reserved. www.familydog.com | (Courtesy of the Fine Arts Museums of San Francisco)

At the Summer of Love's height, more than one million posters were reportedly being printed and snatched up by Bay Area locals and farther-flung collectors. The intricate and trippy designs became a secret language, discernable only to those who were "tuned in" to the lingo.

"The proliferation of messages encoded in a rock poster's image ensured that the eye of the initiate would keep circling across the printed page, as his or her mind struggled to comprehend," Terry writes in an essay for the exhibition's catalog, Selling San Francisco's Sound: Artistry in 1960s Rock Posters. "Almost as soon as the message was clear, it receded back into the design and the process of decoding began again."

Of course, the "secret messages" weren't along the lines of "Knock twice to enter." It was more about the less-than-direct delivery of the basic details of the show.

Until then, straightforward concert or performance playbills had been the norm. But in the Summer of Love, the show's information was literally part of the design, meaning you had to stop and stare to puzzle out who was playing where and when. To put it all together, you had to pause, explore, and look beyond — a metaphor for the larger ideals of the Summer of Love.

Joe Gomez, "'Optical Occlusion,' Big Brother and the Holding Company, Mt. Rushmore, November 23–25, Avalon Ballroom," 1967. Color offset lithograph poster. Fine Arts Museums of San Francisco, Museum purchase, Achenbach Foundation for Graphic Arts Endowment Fund, 1974.13.171. Artwork by Joe Gomez. © 1966, 1984, 1994 Rhino Entertainment Company. Used with permission. All rights reserved. www.familydog.com | (Courtesy of the Fine Arts Museums of San Francisco)

Victor Moscoso, "'Incredible Poetry Reading,' Ferlinghetti, Wieners, Meltzer, Whalen, Welch, McClure, Ginsberg, June 8, Norse Auditorium," 1968. Color offset lithograph "animated" poster. Fine Arts Museums of San Francisco, Gift of the Gary Westford Collection, in Honor of Victor Moscoso and All the Poets. © Victor Moscoso | (Courtesy of the Fine Arts Museums of San Francisco)

San Francisco's artists developed their poster designs within brain-trust collectives like the Family Dog — a commune and promotions company started in 1966 by Chet Helms — with shoe-string budgets and, often, on mind-tripping drugs such as peyote and LSD.

From about 1965, when some of the first posters were printed, until the tail end of the '60s, the Bay Area's rock posters were much more than mere ads or mementos. They declared allegiance to the Summer of Love's ideals of freedom of thought and expression. And their groundbreaking look would become a hallmark of that halcyon summer.

"The genesis of the uniquely Bay Area strain of the rock poster genre can readily be considered within the realm of 1960s visual culture," Terry writes in her essay. "Though their inspiration varied, the poster artists, like their fine art peers, created works indisputably of their era, teeming with the preoccupations of the day."

Randy Tuten, "Led Zeppelin, Bonzo Dog Band, Rahsaan Roland Kirk His Vibration Society, November 6–8, Winterland, Rolling Stones, November 9, Oakland Coliseum," 1969. Color offset lithograph poster. Fine Arts Museums of San Francisco, Museum purchase, Achenbach Foundation for Graphic Arts Endowment Fund, 1972.53.219. © Bill Graham Archives, LLC. All Rights Reserved | (Courtesy of the Fine Arts Museums of San Francisco)

Wilfried Sätty, "Turn on Your Mind (Jerry Garcia Wearing Flag Top Hat)," ca. 1967. Color offset lithograph poster. Fine Arts Museums of San Francisco, Gift of Walter and Josephine Landor, 2001.97.29A. © Walter Medeiros / Sätty Estate | (Courtesy of the Fine Arts Museums of San Francisco)

While the seasons changed on the Summer of Love, its impact on the zeitgeist was indisputable.

"When the music ended and the lights came on, what remained was a series of innovative graphics that could instantly transport the scene's participants back to a time and place," Terry writes in her essay, "where creative freedom mingled with the rarefied idealism for which San Francisco continues to be known."

"Krishna Consciousness Comes West: Swami Bhaktivedanta, Allen Ginsberg, The Grateful Dead, Moby Grape, Big Brother The Holding Company, Mantra Rock Dance, January 29, Avalon Ballroom," 1967. Color offset lithograph handbill. Collection of John J. Lyons | (Courtesy of the Fine Arts Museums of San Francisco)

Loren Rehbock, "Mnasidika, 1510 Haight St.," 1967. Color offset lithograph poster. Fine Arts Museums of San Francisco, Gift of the Gary Westford Collection, in memory of Janis Joplin, 2016.32.3. © Loren Rehbock | (Courtesy of the Fine Arts Museums of San Francisco)

Larry Stark, "'Rorschach Test II,' Frumius Bandersnatch [sic], Clear Light, Buddy Guy, June 14–16, Avalon Ballroom," 1968. Offset lithograph poster. Fine Arts Museums of San Francisco, Museum purchase, Achenbach Foundation for Graphic Arts Endowment Fund, 1974.13.139. Artwork by Larry Stark. © 1966, 1984, 1994 Rhino Entertainment Company. Used with permission. All rights reserved. www.familydog.com | (Courtesy of the Fine Arts Museums of San Francisco)

**The Summer of Love Experience is on exhibit at the Fine Arts Museums of San Francisco's de Young, through Aug. 20.**