Of all the Family Dog posters, FD-24 may be the most purely beautiful — Stanley Mouse and Alton Kelley's "Tree House," a bird's clawed foot rising out of the ground on a tangle of vine and root to cradle an airborne cabin. It announced the 13th Floor Elevators and the Sir Douglas Quintet at the Avalon Ballroom, September 2 and 3, 1966.

Friday, September 2 was opening night — and it was also the week the Elevators finally turned up.

Six days earlier, the same band had been the headline act printed across Wes Wilson's BG-25 for a weekend at the Fillmore, and had not appeared at all. The Fillmore listings record the whole substitution in flat prose: scheduled, did not play, replaced by Quicksilver on the Friday and Country Joe & the Fish on the Saturday. Whatever kept them off Bill Graham's stage — and the record does not say — it had cleared by the following weekend, because the Family Dog's listings put them at the Avalon on the 2nd and 3rd with their name at the top of their own poster.

They were among the very few out-of-town bands the San Francisco scene took fully as its own. Roky Erickson's voice, Tommy Hall's amplified electric jug burbling underneath everything, and a band that had put the word "psychedelic" on an album cover in 1966 before most of the Bay Area had settled on what to call any of it — the Elevators came from Austin with the thing already fully formed. Second-billed was another Texas act, Doug Sahm's Sir Douglas Quintet, whose "She's About a Mover" had charted the year before and who had relocated to California. Two Texas bands on a San Francisco poster, on one of the best sheets Mouse and Kelley ever drew.

The Fillmore had its own bill the same night: Wes Wilson's BG-26, with Jefferson Airplane, the PH Factor Jug Band and Andrew Staples. It is worth being precise here, because the BG-26 sheet is one poster covering four nights — September 2 through 5 — and the bills rotated underneath it. September 2 and 3 were the Airplane's. September 4 belonged to the Grateful Dead, over Quicksilver Messenger Service and Country Joe & the Fish, and the Fillmore Auditorium listings attach a note to that date worth quoting rather than paraphrasing: "First Time GD Headlines At The Fillmore." September 5, Labor Day, closed the run with Martha & the Vandellas. One sheet, four nights, three completely different headliners — which is why the advertised run and any single night's bill are not the same thing. (A separate date is sometimes conflated with the September 4 one: the December 9–11, 1966 weekend, when the Dead headlined over Big Mama Thornton and Tim Rose. Both are documented; the venue's own record marks September as the earlier.)

What is not in doubt is where the Dead were on September 2 itself, and it is a better story than the myth. They were not at the Fillmore. They were twenty miles down the Peninsula in Hillsborough, playing a private debutante ball for sisters Ayn and Lyn Mattei at La Dolphine, a mansion on Manor Drive — the full band, Garcia, Weir, Lesh, Kreutzmann and Pigpen, set up on a dance platform in the formal garden while a separate orchestra under Al Trobbe played for the adults inside the ballroom. They were loud enough that neighbors complained and the band had to be moved indoors. In September 1966 the Grateful Dead were still a group you could hire for a coming-out party, and still loud enough to get thrown out of the garden.

So September 2, 1966 gives us two Texas bands on Mouse and Kelley's most graceful poster at the Avalon, the Airplane on Wilson's at the Fillmore, and the Dead in a rich family's back yard in Hillsborough being asked to come inside. The hero, oldest-anchored, is the Tree House — and the band on it showed up this time.