On the third weekend of September 1966, Bill Graham hung a Wes Wilson poster in the windows of the Fillmore Auditorium and, in doing so, quietly demonstrated the trick that would make him famous: bait the marquee with a rock band, then feed the crowd something it did not know it wanted. The headliner was the Byrds — Los Angeles' jangling, Rickenbacker-driven answer to the British Invasion, riding the afterglow of "Eight Miles High" and its attendant radio trouble. Beneath them on the bill sat a San Francisco group called the Wildflower and, per Wolfgang's catalog listing for the poster, a third act billed as New Stage. Folded into the same night was something stranger: a staging of "The Dutchman," LeRoi Jones's incendiary one-act about a fatal encounter on a subway car (per the poster's own copy, echoed in the collector literature).

The poster is catalogued as BG-28, the twenty-eighth in Graham's numbered Fillmore series, and it is the work of Wes Wilson — the designer usually credited with inventing the melting, near-illegible psychedelic lettering that defined the era. BG-28 is a comparatively restrained Wilson: a photograph of the Byrds placed in an oddly pastoral setting rather than the flame-alphabet he would soon make inescapable. It survives today in first, second, and third printings, with Wolfgang's offering originals alongside a 2022 reprint, and it is corroborated on the Rock Poster Society's site and in Recordmecca's archive — a well-attested artifact, not a rumor.

The poster is dated Friday, September 16, 1966. But Graham's Fillmore weekends were Friday-and-Saturday affairs, and this engagement ran into Saturday the 17th — which is how the show lands on this date at all. It is worth being honest that the printed sheet names only the 16th; the second night is the near-universal collector and archival reading of a Graham Fillmore weekend rather than a line of type on the poster itself (the COAU Fillmore list carries a September 17 Byrds entry, corroborating the Saturday). If you stood in that room on the 17th, you were watching the exact experiment Graham liked to boast about later — that a theater piece by Jones would have drawn a handful of people on its own, and drew hundreds only because he had stapled a hit band above it.

What makes the night resonant is the collision it stages. This is the San Francisco scene catching a Southern California band at the hinge of its career, in a hall that was itself only months into its life as the epicenter of American psychedelia. The Byrds would fracture and re-form repeatedly over the next two years; the Fillmore would grow into the template every other city copied; and Wes Wilson would, within the year, leave Graham's employ in a dispute over pay — a reminder that the posters we now frame as fine art were, at the time, piecework. On September 17, 1966, all of that is still ahead. What exists is a Saturday night, a Rickenbacker, a light show, and a play about a subway, held together by a sheet of paper with Wilson's name in the corner.

A note for the skeptical: the same date carries other, thinner claims across the decade. Jefferson Airplane were mid-residency at the Matrix on Friday, September 17, 1965, in the club that served as their home base — the night Corry Arnold suspects Bob Harvey first plugged in an electric bass, with JC Burris booked but a no-show after the Thursday (per rockprosopography101, carrying Arnold's own hedges). Little Richard brought an all-soul revue to the Straight Theater on Sunday, September 17, 1967 — and the COAU cache's "Monday" label for that date is simply wrong; September 17, 1967 was a Sunday. And the Family Dog ran a barely-documented "film orgy" on the Great Highway (FD-690917) on Wednesday, September 17, 1969, which Corry Arnold (Rock Archaeology 101) treats as an undocumented "Film and Light Spectacular" with no eyewitnesses. All real, all worth a footnote. But only one of them left a numbered poster by one of the Big Five, and that is why the Byrds' weekend at the Fillmore is the anchor.