The Summer of Love was a social phenomenon that occurred during the summer of 1967, when as many as 100,000 people converged on the Haight-Ashbury neighborhood of San Francisco, thus initiating a major cultural and political shift. While hippies also gathered in New York, Los Angeles, Philadelphia, Seattle, Portland, Washington, D.C., Chicago, Miami, Montreal, Toronto, Vancouver, and across Europe, San Francisco was the center of the hippie revolution,a melting pot of music, psychoactive drugs, sexual freedom, creative expression, and politics. The Summer of Love became a defining moment of the 1960s, as the hippie counterculture movement came into public awareness. This unprecedented gathering of young people is often considered to have been a social experiment, because of alternative lifestyles that became common, both during the summer itself and during subsequent years. These lifestyles included communal living; the free and communal sharing of resources, often among total strangers; and free love.
In contrast, the summer of 1967 also saw some of the worst violence in US cities in the country's history — this was because of the race riots/insurrections that occurred in places such as Detroit and Newark. This aspect of the summer of 1967 is often called "The Long, Hot Summer". The cause of this violence is generally attributed to racial discrimination against African-Americans and the frustration and anger it inspired in black people.
Inspired by the Beats of the Fifties, who declared themselves independent from the alleged authoritarian order of America, the Haight-Ashbury community rested on a rejection of American commercialism. Haight residents eschewed the material benefits of modern life, encouraged by the distribution of free food and organized shelter by the Diggers, and the creation of institutions such as the Free Clinic for medical treatment. Psychedelic drug use became but one means to find a new reality. Grateful Dead guitarist Bob Weir comments:
'Haight Ashbury was a ghetto of bohemians who wanted to do anything - and we did but I don't think it has happened since. Yes there was LSD. But Haight Ashbury was not about drugs. It was about exploration, finding new ways of expression, being aware of one's existence.'
The prelude to the Summer of Love was the Human Be-In at Golden Gate Park on January 14, 1967, which was produced and organized by artist Michael Bowen as a "gathering of tribes". The event was announced by the Haight-Ashbury's own psychedelic newspaper, the San Francisco Oracle: "A new concept of celebrations beneath the human underground must emerge, become conscious, and be shared, so a revolution can be formed with a renaissance of compassion, awareness, and love, and the revelation of unity for all mankind." 
The gathering of approximately 30,000 like-minded people made the Human Be-In the first event that confirmed there was a viable hippie scene.
The term "Summer of Love" originated with the formation of the Council for the Summer of Love in the spring of 1967 as response to the convergence of young people on the Haight-Ashbury district. The Council was composed of The Family Dog, The Straight Theatre, The Diggers, The San Francisco Oracle, and approximately twenty-five other people, who sought to alleviate some of the problems anticipated from the influx of people expected in the summer. The Council supported the Free Clinic and organized housing, food, sanitation, music and arts, and coordination with local churches and other social groups. The ever-increasing numbers of youth making a pilgrimage to the Haight-Ashbury district alarmed the San Francisco authorities, whose public stance was that they would keep the hippies away. Adam Kneeman, a long-time resident of the Haight-Ashbury, recalls that the police did little to help; organization of the hordes of newcomers fell to the overwhelmed residents themselves.
College and high-school students began streaming into the Haight during the spring break of 1967. San Francisco's government leaders, determined to stop the influx of young people once schools let out for the summer, unwittingly brought additional attention to the scene, and an ongoing series of articles in local papers alerted the national media to the hippies' growing numbers. By spring, Haight community leaders responded by forming the Council of the Summer of Love, giving the word-of-mouth event an official-sounding name. The mainstream media's coverage of hippie life in the Haight-Ashbury drew the attention of youth from all over America. Hunter S. Thompson labeled the district "Hashbury" in The New York Times Magazine, and the activities in the area were reported almost daily.
The movement was also fed by the counterculture's own media, particularly the San Francisco Oracle, whose pass-around readership is thought to have topped a half-million at its peak that year. The media's fascination with the "counterculture" continued with the Monterey Pop Festival in June 1967, where approximately 30,000 people gathered for the first day of the music festival, with the number swelling to 60,000 on the final day. The song "San Francisco (Be Sure to Wear Flowers in Your Hair)" written by John Phillips of The Mamas & the Papas and sung by Scott McKenzie was initially designed to promote the Monterey Pop Festival:
“ If you're going to San Francisco,
be sure to wear some flowers in your hair...
If you're going to San Francisco,
You're gonna meet some gentle people there. ”
"San Francisco" became an instant hit (#4 in the U.S., #1 in the UK) and quickly transcended its original purpose by popularizing an idealized image of San Francisco. In addition, media coverage of the Monterey Pop Festival facilitated the Summer of Love, since large numbers of fledgling hippies headed to San Francisco to hear their favorite bands, among them the The Doors, Grateful Dead, Jefferson Airplane, Quicksilver Messenger Service, The Jimi Hendrix Experience, Otis Redding, The Byrds, and Big Brother and the Holding Company with Janis Joplin.
During the Summer of Love, as many as 100,000 young people from around the world flocked to San Francisco's Haight-Ashbury district, as well as to nearby Berkeley and to other San Francisco Bay Area cities, to join in a popularized version of the hippie experience. Free food, free drugs and free love were available in Golden Gate Park, a Free Clinic (whose work continues today) was established for medical treatment, and a Free Store gave away basic necessities to anyone who needed them. The Summer of Love attracted a wide range of people of various ages: teenagers and college students drawn by their peers and the allure of joining a cultural utopia; middle-class vacationers; and even partying military personnel from bases within driving distance. The Haight-Ashbury could not accommodate this rapid influx of people, and the neighborhood scene quickly deteriorated. Overcrowding, homelessness, hunger, drug problems, and crime afflicted the neighborhood. Many people left in the fall to resume their college studies.
On October 6, 1967, those remaining in the Haight staged a mock funeral, "The Death of the Hippie" ceremony, to signal the end of the played-out scene. Mary Kasper explained the message of the mock funeral as follows: “ We wanted to signal that this was the end of it, don't come out. Stay where you are! Bring the revolution to where you live. Don't come here because it's over and done with. ”
When the newly-recruited Flower Children returned home, they brought new ideas, ideals, behaviors, and styles of fashion to many major cities in the U.S., Canada, Western Europe, Australia, New Zealand, and Japan.The phrase "Summer of Love" (or, more accurately, the "Second Summer of Love") is sometimes used (particularly in the UK) to refer to the summers of 1988 and 1989 and the rise of Acid House music and rave culture. On September 2, 2007, San Francisco celebrated the 40th anniversary of the Summer of Love. The 40th anniversary was also celebrated at various locations in the UK including Hawkhurst in Kent, where a small mini-festival was held on 07/07/07. The special guest that day was Barry Melton, "the Fish" of Country Joe and the Fish fame.