It was organized by John Chambliss, a UW philosophy professor and others from the Blue Moon tavern in the U-District who were anti-war and anti-US imperialism.
Weren't Jimi Hendrix and Janis Joplin also there?  Maybe Merrilee Rush?  It happened at Betty Nelson's raspberry farm just off the Ben Howard Road.  !968 was an historic year.  LBJ quit when he knew the Vietnam War was unwinnable.  King and Kennedy were assassinated and then the police riot at the DNC convention in Chicago.  SDS and the Black Panthers were active.  Nixon came back after an humiliating defeat by Pat Brown in California.