Friday, August 16, 1968 is the San Francisco ballroom scene's rival-twins pattern in its purest form. Across town from each other, the two great rooms opened weekend stands the same night. At Fillmore West, the second bracket of BG-133 began: Creedence Clearwater Revival — months from "Proud Mary," still a Bay Area band on the cusp — over It's a Beautiful Day and the Texas blues of Albert Collins (the bill order per the Bill Graham Foundation's Aug-16 page, which files all three under BG-133). At the Avalon, Chet Helms's Family Dog answered with FD-133: Bill Haley and the Comets — the man who'd put "Rock Around the Clock" into the world fourteen years earlier — with the Drifters and the young Flamin' Groovies beneath him, the poster by Jerry Wainwright and George Hunter with Vulcan Lights (per wolfgangs, which credits both artists and brackets the run Aug 16–18). One room bet on the scene's future; the other, on its roots — the same Friday night, a mile apart.

A year later, on Saturday, August 16, 1969, the second day of Woodstock belonged substantially to San Francisco. Santana — barely recorded, about to be made by this one afternoon — played a little after two; the Grateful Dead took the stage late that night; and Creedence, a year on from that Fillmore West bracket above, followed after midnight (performance times per the Woodstock festival record on wikipedia, corroborated against setlist.fm). The bands the ballrooms had built were, that day, the festival's spine.