The station at 98.9 was established in February 1948 as the FM simulcast component of KJBS 1100 (now KFAX) by Julius Brunton & Sons, transmitting from the (still existing) tower atop Clay Jones Apartments at 1250 Jones Street. As KJBS it had been a full-service station with news, weather, and sports programming, and served as a relay, interrupting programming overnight, to alert police and fire personnel to incidents, prior to the departments' own radio dispatch systems. The FM station was financially unsuccessful, and in 1953 it was sold to CBS. KCBS-FM had been operating with substantially lower power on 103.7 when it made the move to acquire this station.