Jam session at the Athletic Field across the street from the festival. Just listing this as Garcia as it seems unlikely the full band performed here.

hooterollin: Grateful Dead Performance List January-June 1967

lostlivedead: May-June 1967 Grateful Dead Itinerary Overview (comment) As per Rock Scully, "We set up a stage and, after the shows, the various bands would put on jam sessions. Jimi Hendrix, Eric Burdon, Jerry Garcia, Phil Lesh, the Airplane... We all took acid together and played all night."

lostlivedead: May-June 1967 Grateful Dead Itinerary Overview

deadessays: Deadbase Corrections