550 kHz was the longtime home of KOY, the first radio station in Arizona. It moved here from 1390 kHz. The FCC granted the station a power increase to 5000 watts days and 1000 watts nights in 1949. KOY was affiliated with CBS and was the flagship station for the Arizona Radio Network. It became a Mutual affiliate in the mid-'50s, swapping affiliations with KOOL 960 kHz. It became an ABC affiliate in 1958, which lasted until 1971. KOY was the NBC affiliate from 1982 to 1987, where it joined the ABC Entertainment network.

When the era of network radio entertainment ended in the late 1950s, KOY became a middle-of-the-road (MOR) formatted station catering to older listeners. That format, now called Adult Standards, remains KOY's format to this day.

KOY has changed owners several times over the years, from station founder Earl Nielsen, to the Prairie Farmer magazine (using the corporate name "Salt River Broadcasting Company" - the company also owned WLS in Chicago until 1954) to today's Clear Channel (formerly known as Chancellor Media and AMFM, inc.). It was AMFM's purchase of the studios, format, and personnel of KGME that forced KOY to move to 1230 kHz, replacing classic-country KISO.

The history of KOY can be found here.

KGME Sportsradio 550 was originally on 1360 kHz. It stayed on 550 for about a year and a half before swapping frequencies with KFYI and moving to 910 kHz.

KFYI is a news/talk station affiliated with CBS and Fox News Radio. Its politics are considered extremely conservative.

The 550 transmitter site is near 36th St. & Southern Ave. in southeast Phoenix. This site was opened in the late 1960s. Its original home was at 12th St. & Camelback Rd. in north central Phoenix starting in 1937.