Part of 1977's Terrapin Station and written in the late seventies by Bob Weir and John Perry, the song is about bugged eyed, drugged out, messianic dudes who used to hang out at the stage door of every Dead concert. And it wasn't Jerry Garcia.
Such men need to rave and Bob lets him rave on with pseudo-spiritual old testament verbiage about waters parting before him, wheels in the sky and "my words fill sky with flame".
The California part seems especially appropriate since all such crazies seemed to emanate from the left coast during these times. You don't see these guys too often these days and it makes you wonder what happened to them.