KIOI (101.3 FM, "Star 101.3") is a hot AC-formatted radio station licensed to San Francisco, California and owned by iHeartMedia, Inc. The radio studios and offices are in the SoMa district of San Francisco. KIOI has an effective radiated power (ERP) of 125,000 watts. It is considered a "superpower station" due to this unusually high wattage that is grandfathered into KIOI's license. It is one of two stations in San Francisco broadcasting with more than 100,000 watts, the other being KQED-FM, at 110,000 watts. KIOI's transmitter is on Radio Road in Daly City, amid the towers for other San Francisco-area FM and TV stations. It also has booster stations on 101.3 MHz in Walnut Creek and Pleasanton. KPEN KIOI was first licensed in 1957 as KPEN, licensed to the San Francisco Peninsula community of Atherton, California by James Gabbert, a Stanford University engineering major, fellow student Gary M. Gielow, and realtor John S. Wickett, doing business as Peninsula FM. The station was assigned to 101.3 FM, a frequency which had been vacated two years earlier with the deletion of the Oakland Tribune newspaper's KLX-FM, which had begun broadcasting May 3, 1948, simulcasting sister station KLX's programming 17 of the 18 hours it was on daily. KLX-FM was deleted on October 10, 1955. KPEN debuted on October 27, 1957, with 1,500 watts from a transmitter located on Kings Mountain in the Santa Cruz Mountains. Unusual for the era, KPEN was not affiliated with any stations on the AM band, which meant it had to have 100% original programming. The station put an emphasis on high audio quality, in contrast to other FM stations that did not take advantage of FM broadcasting capabilities. During the day, KPEN played mostly orchestral pop music, switched to a lighter blend of background "dinner music" in the early evening, then classical music after 8. Eventually Gabbert and Gielow hosted an evening program called Excursions in Sound, which showcased high fidelity recordings and took advantage of the high quality broadcast signal. Two years after KPEN's successful debut, the transmitter was moved to San Bruno Mountain and power increased to 35,000 watts. Then, on August 14, 1964, power was further increased to 125,000 watts, making it the most powerful signal west of the Mississippi River (it was grandfathered in at that power level by the Federal Communications Commission (FCC), which capped stations in that part of the country