It should be noted that before it became the powerhouse CHR that it is best known as, it went from top-40 to AC when it was combined with 1150 and changed call letters from KKDJ -- the disaster that was "K-double I-S" -- and was also a disco station during that genre's era of popularity.
If we are celebrating KIIS-FM as a CHR, the logical starting point is actually the summer of 1981, when they hired Rick Dees.