Short answers, pulled from the story.
The first printed use of hippie appeared on the 27th of April 1961 in an article by Norman Mailer questioning President Kennedy's behavior. The term emerged from jazz slang of 1940s Harlem where musicians used terms like hip and hep to describe someone sophisticated or up-to-date.
Twenty thousand to thirty thousand hippies gathered in San Francisco's Golden Gate Park for the Human Be-In on the 14th of January 1967 organized by Michael Bowen. Scott McKenzie's rendition of John Phillips' song San Francisco became a hit that inspired thousands to travel to California wearing flowers in their hair.
Over five hundred thousand people attended Woodstock Music and Art Fair in Bethel New York from August 15 to 18 1969 featuring bands like Jimi Hendrix and Janis Joplin. Three hundred thousand gathered at Altamont Free Concert about forty-five kilometers east of San Francisco in December 1969 where Rolling Stones performed with Hells Angels providing security.
Stephen Gaskin founded Monday Night Class in 1966 that attracted fifteen hundred followers discussing Christian Buddhist and Hindu teachings before establishing Tennessee community called The Farm in 1970. Timothy Leary established League for Spiritual Discovery on the 19th of September 1966 declaring LSD as holy sacrament based on freedom of religion argument.
Mainstream media lost interest in hippie counterculture during mid-late 1970s as psychedelic rock declined and new genres like disco punk emerged. Hippie communes continued flourishing with Tawapa community founded in New Mexico in 1970 lasting until 1990s when housing developments pushed people off land.