For three days in June 1967, the Monterey County Fairgrounds held the festival that everything after would be measured against.

Monterey Pop was the first of its kind — the rock festival as the world would come to know it — organized by John Phillips of the Mamas and the Papas, producer Lou Adler, and publicist Derek Taylor. Over June 16, 17, and 18, it introduced America to a run of performances that would become legend: the first major American appearances of the Jimi Hendrix Experience and the Who, the large-scale breakout of Janis Joplin with Big Brother and the Holding Company, and Otis Redding playing to a vast, mostly white rock audience for the first time. Ravi Shankar played an entire Sunday afternoon. The Grateful Dead, Jefferson Airplane, the Byrds, Buffalo Springfield, Simon and Garfunkel, Country Joe and the Fish, the Butterfield Blues Band, Eric Burdon and the Animals, Quicksilver Messenger Service — the bill reads like a census of the moment.

The poster is its own artifact. Tom Wilkes designed it and had it printed on silver foil stock, sold at the festival itself — a piece built to be kept. It carried the festival's gentle, era-defining motto and the dates that would mark, as much as any single weekend can, the opening of the Summer of Love.

If the Red Dog Saloon two years earlier was the seed, Monterey was the bloom — the moment the San Francisco underground walked out onto a national stage and the rest of the country leaned in to look.