On Thursday, September 26, 1968, the Fillmore West bill read like the live cover of a record that had not quite finished being made: Mike Bloomfield and Al Kooper & Friends, headlining a three-night stand over It's a Beautiful Day and the Loading Zone, lights by Holy See (per the Grateful Dead Archive Online's record of the poster, Wolfgang's, and chickenonaunicycle's Fillmore West list). The engagement ran Thursday through Saturday, September 26–28, 1968.

The context is what makes the night. Earlier that year Bloomfield — the Chicago-schooled guitarist who had electrified Dylan at Newport, then built the Paul Butterfield Blues Band and the Electric Flag — had gone into a Columbia studio with organist Al Kooper for a loose, half-improvised session that became Super Session, one of the best-selling and most influential albums of 1968. Bloomfield, a chronic insomniac, had famously bailed after a single day; Kooper finished the record with Stephen Stills. The album's success created an immediate demand for a thing that did not really exist — a Bloomfield-Kooper live band — and the pair set out to manufacture it on stage. The Fillmore West run was part of that effort. The recordings made across these San Francisco nights were released in early 1969 as The Live Adventures of Mike Bloomfield and Al Kooper, a double LP that captured exactly the ragged, generous, sometimes shambolic quality of two virtuosos assembling a set in front of a paying audience.

The poster, BG-138 in Graham's series, is the work of Lee Conklin, whose densely metamorphic pen-and-ink style — faces dissolving into animals dissolving into machinery — was reaching its peak across 1968 (GDAO item 390850 credits Conklin and gives the September 26–28 dates and the full bill; Wolfgang's and multiple dealer records agree). Conklin's Fillmore posters from this stretch are among the most intricate in the whole series, closer to the underground comics tradition than to the Art Nouveau lettering of the ballroom's opening years.

Beneath the headliners, the bill is pure San Francisco 1968. It's a Beautiful Day, the David LaFlamme band whose violin-driven "White Bird" would define them within a year, was on the rise; the Loading Zone, from across the Bay in Berkeley, brought the soul-rock end of the local spectrum. The result was a bill that ran from Chicago blues-rock virtuosity at the top down through a distinctly Bay Area sound underneath — the kind of programming Graham did almost reflexively.

A note on billing and on the limits of the source: the poster and the archive records are consistent on the bill and the dates, and the live album is independent proof that the run happened and was recorded. What the poster cannot tell us is the exact shape of any single night — Bloomfield's attendance was never guaranteed, and "and Friends" was doing real work in the billing, covering a rotating cast of sidemen. This is one to describe as a run and a record, not to pin to a fixed set on the 26th.

September 26 across the other timeline years is quieter. In 1969 the day fell inside a different Fillmore West run — Chuck Berry's, on the Greg Irons BG-193 poster — but the antagonist flag there is worth carrying forward: the Berry September run is BG-193, not the January 1969 Chuck Berry poster BG-158 (a Randy Tuten design for a Bloomfield-shared bill), a genuinely easy pair to confuse. The same 1969 Friday also saw the Flamin' Groovies play the old Fillmore Auditorium, but chickenonaunicycle explicitly flags that as a non-Bill-Graham rental, outside the numbered BG series, and no poster for it could be confirmed from the reachable archives. In 1965, 1966, and 1967 there was no documented psychedelic-ballroom event on the 26th — only Matrix club dates and, in 1967, a film night at the Straight Theater. That leaves the 1968 Bloomfield-Kooper stand as the unambiguous anchor for the day: the live counterpart to Super Session, announced by one of Lee Conklin's finest posters.