The Great Society played its last show on September 11, 1966

"September 11, 1966 Fillmore Auditorium, San Francisco
Jon Hendricks Trio/Elvin Jones/Joe Henderson Quartet/Big Mama Thornton/Denny Zeitlin Trio/Jefferson Airplane/Great Society/Wildflower
Benefit for Both/And jazz club.

Great Society lead singer Grace Slick’s star quality is obvious to the Airplane, too, and she seems like the ideal replacement for Signe Andersen. After her marriage to Airplane light show man Jerry Andersen, new mom Signe is under pressure to retire from performing. At this show, Jack Casady approaches Grace Slick about replacing Andersen in the Airplane, and she agrees to join."
http://rockprosopography101.blogspot.ca/2009/07/may-september-1966-jefferson-airplane.html

The set that the Airplane played was totally successful. Guitarist Jorma Kaukonen's blues solo and vocal on "Kansas City," the duet between Jorma and bassist Jack Cassady...
http://deadsources.blogspot.ca/2012/02/september-11-1966-jazzrock-show.html

http://www.dead.net/show/september-11-1966

https://www.google.ca/search?q=The+Great+Society

"The Great Society had recorded an early version of "Somebody to Love" (under the title "Someone to Love") as the B-side of their only single, "Free Advice", produced by Sylvester Stewart (soon to become famous as Sly Stone). It reportedly took more than 50 takes to achieve a satisfactory rendition. The Great Society decided to split up in late 1966 and played its last show on September 11. Soon after, Slick was asked to join Jefferson Airplane by Jack Casady (whose musicianship was a major influence on her decision) and her Great Society contract was bought out for $750."
https://en.wikipedia.org/wiki/Jefferson_Airplane#Commercial_breakthrough

9/11