About KPIX CBS 5KPIX signed on the air on December 22, 1948, the first television station in Northern California as well as the 49th in the United States. It was originally owned by Associated Broadcasters, owners of KSFO (560 AM). Initially, channel 5's signal was transmitted from a tower on top of the Mark Hopkins Hotel on Nob Hill. It later moved to a shared transmitter tower with KGO-TV (channel 7) at the Sutro Mansion (which was located midway between Mount Sutro and Twin Peaks), and then to the Sutro Tower in 1973. KPIX's first studio was in the attic of the Mark Hopkins Hotel (just above the "Top of the Mark").
The station immediately joined CBS due to a deal KSFO's owners had worked out with the television network one year earlier. KSFO was CBS radio's Bay Area affiliate from 1937 to 1941, when Associated Broadcasters backed out of a deal for CBS to buy the station. When KSFO was still affiliated with CBS, it was originally slated to move to 740 AM, the dial position of San Jose's KQW. 740 AM was the last 50,000-watt frequency available in the Bay Area, and KSFO was to raise its power to 50,000 watts after moving to 740. However, after KSFO parted ways with CBS radio, the network moved its Bay Area affiliation to KQW and was not about to give up the advantage of owning the Bay Area's last available 50,000-watt station. After lengthy Federal Communications Commission (FCC) hearings, KSFO won the 740 frequency, but later decided to stay at 560 and concentrate its efforts on building a television station. It traded the 740 frequency to CBS in return for getting the CBS television affiliation for the Bay Area. KQW remained at 740 and CBS changed its call sign to KCBS.