On Thursday, September 28, 1967, Jefferson Airplane came home. The band that had, more than any other, carried the San Francisco sound out to the rest of the country that summer — Surrealistic Pillow behind them, "Somebody to Love" and "White Rabbit" on the radio all season — played the Fillmore Auditorium at the top of a bill over Mother Earth and the Flamin' Groovies, with Glenn McKay's Head Lights running the projections (per chickenonaunicycle's Fillmore Auditorium list, Wolfgang's, and Corry Arnold's Rock Prosopography chronology of the band). It was the Thursday opening of a weekend that then moved across town to Winterland for Friday and Saturday, September 29–30.

That geography is written into the poster. BG-85, designed by Greg Irons, is a combined-weekend piece: it advertises the Fillmore Auditorium on Thursday the 28th and Winterland on Friday and Saturday the 29th–30th, one artifact covering two rooms (Wolfgang's catalogs BG-85 to Irons; chickenonaunicycle carries the split, and the Winterland list independently shows the Airplane / Mother Earth / Flamin' Groovies pairing on the 29th–30th). It is an important thing to be precise about: BG-85 is not a Fillmore-only poster, and the 28th is only the first of its three nights. The poster tells us the weekend was promoted as a unit; it does not certify who played which room on which night, though the sources are consistent that the Airplane headlined throughout.

The undercard is a good snapshot of the moment. Mother Earth, the blues band built around the enormous voice of Tracy Nelson, had only recently arrived in San Francisco from the Midwest and was quickly becoming a fixture of the ballrooms. The Flamin' Groovies, third-billed here, were San Francisco's own — a band running deliberately against the psychedelic grain, playing tight, roots-driven rock-and-roll while everyone around them stretched out; within two years they would be back at this same Fillmore on their own non-BG rental. Greg Irons, the designer, was near the start of the run of Fillmore work that would define his late-'60s output; BG-85 sits among the earlier pieces in that sequence.

The choice of the Airplane's Fillmore night as the anchor for September 28 is a deliberate one, made over a strong competitor: on the same date in 1968, the Avalon was running the third day — a Saturday — of the Flatt and Scruggs / Jack Elliott / Sons of Champlin / Country Weather stand on Wes Wilson's FD-139 poster (the bluegrass-at-the-ballroom bill that opens this chronicle's September 27 page). That 1968 Avalon show is real, poster-backed, and carried here as the day's leading runner-up; the 1967 Airplane weekend gets the top slot because it is the band at its commercial and cultural peak, playing its hometown room, on a poster that itself tells the story of a two-venue San Francisco weekend.

The remaining years are quiet. In 1969 the 28th was the Sunday closing night of Chuck Berry's Fillmore West run (BG-193) and of a Family Dog on the Great Highway bill, neither adding a new poster to the day. In 1965 and 1966 there was no verifiable San Francisco ballroom event on the date at all — only Matrix club bookings (Billy Roberts in '65; Country Joe and the Fish in '66), which sit outside the poster-ballroom scope this chronicle follows. That leaves the 1967 Jefferson Airplane weekend as the natural center of September 28: the hometown band at full altitude, and a Greg Irons poster that quietly documents how a single San Francisco weekend could span two ballrooms at once.