On the summer solstice - Wednesday, June 21, 1967, the first full week of what the press had already christened the Summer of Love - the Grateful Dead played a free afternoon set on the Polo Field in Golden Gate Park, part of a loose, Diggers-flavored solstice 'Do-In.' It was a sprawling, multi-band happening with stages at opposite ends of the field; the Dead shared the day with Quicksilver Messenger Service and Mad River, among others. The band's lineup that afternoon was its original five - Jerry Garcia, Bob Weir, Phil Lesh, Bill Kreutzmann, and Ron 'Pigpen' McKernan (Mickey Hart wouldn't sit in until that fall) - reportedly joined by an unidentified harmonica player. No tape of the set is known to survive; preservation is eyewitness memory and a fragment of film ('The Way It Was'), which together document the Dead opening with 'Viola Lee Blues' and 'Alligator.' It was the kind of event the SF scene did better than anyone in that window: unticketed, outdoors, civic and chaotic at once, the band playing to a park rather than a ballroom.

This day-page carries an honest asterisk that is itself part of AOR's story. Unlike the rest of the week, June 21, 1967 has no numbered concert poster - it was a free happening, not a Bill Graham or Family Dog ballroom booking, so there is no BG/FD catalog entry and no classicposters image. The Art of Rock catalog is built around posters, but the solstice in the park is too central to the moment to omit; it's featured here as a documented event (per the Grateful Dead show archives and Corry Arnold's research) rather than as a poster. For poster imagery on the 21st, the catalog's poster-backed alternative is the Avalon's FD-124 - Patrick Lofthouse's famous die-cut 'pop-up' poster for Kaleidoscope / Mother Earth / Country Weather, June 21-23, 1968 (held by the Smithsonian and the V&A) - a real June-21 anchor in a different year, available if the page needs a poster rather than a park.