Original 1st printing 14 x 21 & 5/8" concert poster for The Youngbloods, It's a Beautiful Day, and Initial Shock, appearing at the Avalon Ballroom in San Franisco, CA, on 8/29-31/1968. 
 
Art by Roger Weil.  The image is #135 in the Family Dog/Avalon series.
 
The poster is in excellent condition.  Just some very light edgewear.