Summer of Love retrospectives have an obvious appeal. As we listen or read, marvel or gawk, half a century on, septuagenarians get to feel warm and fuzzy, sexagenarians get an afterglow, and their children and grandchildren get to feel smug at how sweet, innocent and silly some people (white people, anyway) used to be. The soundtrack cues itself as Scott McKenzieeternally advises, “If you’re goin’ to San Francisco/Be sure to wear some flowers in your hair,” lyrics written by John Phillips of the Mamas and the Papas in a hit record released in May 1967 as a sort of advance trailer for the Monterey Pop Festival, which the group and their producer, Lou Adler, would produce in June just three hours south of the Bay Area.

The Summer of Love was a media event from the start, which isn’t to say it didn’t happen. “Huge Invasion” was the San Francisco Chronicle’s front-page tag, set above “HIPPIES WARN S.F.” in gigantic letters. Monterey Pop in June was certainly the greatest assembling of pop musical talent to that date. D.A. Pennebaker’s film, released the following year, pours out such a cascade of greatest hits — Jefferson Airplane, Jimi Hendrix with his guitar flambé, The Who, Janis Joplin, Otis Redding and for a touch of the other side of the planet, astoundingly, Ravi Shankar — as to send even the most sardonic observer in search of the word “awesome.” When a blues wail (“Ball and Chain”) rips out of the throat of Janis Joplinlike a sonic volcano and Pennebaker cuts to a shot of Cass Elliott of the Mamas and the Papas, sitting in the audience, as she mouths the single word “Wow,” we are in the presence of something more than a social phenomenon — we are momentarily present at what looks like, sounds like, smells like the spirit of the ‘60s incarnate, the promise of some hitherto unmined, unsuspected depth of heart.

In truth, no one knows how many teenagers hitchhiked and caravanned their way across the country to sample the aura, the sunshine, the controlled substances and fever dreams of the Haight-Ashbury neighborhood adjoining Golden Gate Park that summer. Perhaps 50,000, perhaps 75,000 all told, but no one was conducting a census. Still, such numbers would have inflated the population of San Francisco by some ten percent. The rock concerts were teeming and the tie-dyed colors were streaming. The warnings about incoming barbarism caroming through the straight press only inspired more invaders — and criminal gangs foisting amphetamines and God knows what else on the unwary. Probing journalists found that many of the kids were runaways.

Of the mainstream reporters, only Nicholas von Hoffman of The Washington Post caught the true ambiguity — and the darkness — in a series of profiles later gathered in book form under the title We Are the People Our Parents Warned Us Against. Amid the drug tourism and inhospitable police, there were bad trips, criminal gangs, rapes. That spring, local leafleteers were already warning how commonplace rape had become, committed by some of what they called “Uncle Tim’s Children” (for Leary, the pied piper of LSD) against others:

Rape is as common as bullshit on Haight Street. Kids are starving on The Street. Minds & bodies are being maimed as we watch, a scale model of Vietnam [where 448,800 American troops were posted]….Are you aware that Haight Street is as bad as the squares say it is?

But America in the summer of 1967 was even weirder, more menacing, more apocalyptic than the flower children of the Haight-Ashbury knew or wanted to know. The national weirdness was not all of a piece, though radicals strived mightily to put together a unified mental picture of everything crazy and brilliant that was happening, as if the utopian hope and the ghetto devastation were the Yin and Yang of the same puzzle. While the hippie effusion was casting its ambiguous spell on the West Coast, the ghettoes were boiling. First Newark burst into flame and broken glass; 26 died, 1,400 were arrested. Then, a few days later, Detroit, where by the end 43 people had been killed, most of them black; 1,189 injured; 7,231 arrested; 2,509 stores looted or burned. President Lyndon Johnson, invoking the Insurrection Act of 1807, deployed 4,700 paratroopers from the 82nd and 101st Airborne Divisions, which had fought in Vietnam. ...