Sold to interests controlled by the Prairie Farmer/WLS in 1936, KOY was the Phoenix outlet for CBS radio in the 1930s and 1940s as well as an early home for Steve Allen and Jack Williams, the latter a part of the station from 1929 until his election to Arizona governor in 1966.

In addition to a standard analog transmission, KFYI is simulcast over the second HD subchannel of KYOT (95.5 FM) and streams online via iHeartRadio.

[a] From 1912 to 1927, radio communication in the United States was regulated by the Department of Commerce, and originally there were no formal requirements for stations, most of which operated under Amateur and Experimental licenses, making broadcasts intended for the general public.

In 1921, Earl A. Nielsen, a native of Kansas City, Missouri,[7] received a license for an amateur station, with the call sign 6BBH, located at 115 South 21st Avenue in Phoenix.

[10] Despite this, it was reported that on May 23, 1922, the Nielsen company, operating on the standard amateur radio wavelength of 200 meters (1500 kHz), had conducted what were described as the "first broadcasting tests in the Salt River Valley".

[19] In the fall of 1927, Nielsen opened new studios at Pierce Street and Central Avenue; the $70,000 ($1.23 million in 2023 dollars[20]) building also housed the company's sporting goods division and contained a basement with eight bowling lanes.

[5] On March 1, 1937, KOY joined CBS, marking its second time with that network after a five-month stint in 1932, and several days later, it began using a new transmitter site at 12th Street and Camelback Road.

[29] Burridge Butler's ownership strongly emphasized community involvement and service, in some cases copying successful WLS features as the Christmas Neighbors Club and its country music-oriented Dinnerbell program.

[33] A further power increase to 5,000 watts was initially granted in December 1941, but World War II postponed KOY's plans to make the change until 1948.

[34] Burridge Butler did not live to see the frequency change carried out; he died in April 1948, with ownership of KOY given to three company executives, per his will; one of these was program director John R. "Jack" Williams.

[40] In 1952, KOY filed for a television station on channel 10;[41] in competition with a similar bid from KOOL, and wanting to spare years of comparative hearings, the two parties agreed to a time-sharing proposal.

[49] Southern filed to move the transmitter to its present site at the end of 1967[18] and sold the Camelback land to the Coulter car dealership group.

[50] Gary Edens became KOY's general manager in 1970 and helped bring Williams back to a part-time role at the station, hosting a taped version of his previous Yours Sincerely program, which would not discuss state government issues.

In 1983 and 1984, KOY was the broadcast home of the Arizona Wranglers of the United States Football League, though it lost money carrying the nascent team's games.

Three years later, Edens was appointed president of the company's broadcast division, which was renamed Harte-Hanks Radio and relocated its corporate headquarters from Winston-Salem to Phoenix.

KOY-FM split off as an adult top 40 station under the "Y-95" moniker in July 1987, with AM and FM only sharing Bill Heywood's morning show.

[64] Sundance Broadcasting acquired the Edens Phoenix stations in 1993, creating a four-station cluster with KOY, 95.5 (which was relaunched as "rhythm and rock" KYOT), KZON (101.5 FM), and KISO (1230 AM).

Clear Channel opted to sell four of AMFM's FM stations in Phoenix and retain all of its local AMs, including KGME at 550 and KFYI at 910.

[69] In conjunction with the swap, KFYI debuted a morning show hosted by former KTVK anchor Heidi Fogelsong and Jim Sharpe.