Original 1st printing 14 x 20" concert poster for 1960's pop-folk-rockers the Grass Roots appearing along with the Sons of Adam and Big Brother & the Holding Company (before Janis joined) at the Avalon Ballroom in San Francisco, CA on 4/29-30/1966* (show canceled).
Art by (and SIGNED in white pen by) Wes Wilson (central image borrowed from Franz (Von) Stuck), image ("Sin Dance") is # 6 in the Family Dog/Avalon series.
Medium-thick flat vellum stock poster is in absolutely fantastic near mint to excellent (A-/B+ to B+) condition; aside from a few small creases/bends in the extreme lower right margin (about 1&1/2", looks like a small pressure crease), a whisper of edge toning and a couple of negligible edge dings (including a small pinch bend in the top center margin) this is a nearly-unbeatable ARTIST-SIGNED example of this VERY early Avalon poster. GORGEOUS!!!