[9][10] He once explained that he began the broadcasts in order to provide something to listen to for those customers who had constructed receivers from parts purchased for their radio shack.

[11] Christian began making broadcasts with a five-watt vacuum-tube transmitter, operating on the standard amateur wavelength of 200 meters (1500 kHz).

However, effective December 1, 1921, the Department of Commerce, regulators of radio at this time, adopted a regulation that formally created a broadcasting station category, and stations were now required to hold a Limited Commercial license authorizing operation on wavelengths of 360 meters (833 kHz) for "entertainment" broadcasts or 485 meters (619 kHz) for "market and weather reports".

On December 8, 1921, the Electric Lighting Supply Company was issued a broadcasting station license with the randomly assigned call letters KGC, the second in the county after KQL,[14] authorizing operation on the 360-meter entertainment wavelength.

On May 4 the Los Angeles Times reported that a total of seven local stations were slated to make broadcasts that day, comprising a schedule that ran from noon to 9:00 p.m., with KGC assigned 2:00-2:30 and 7:30-8:00 p.m.[16][17] On May 4, 1922, the Electric Lighting Supply Company was issued a broadcasting license for a station with the randomly assigned call letters of KNX, also on 360 meters, and located at the company's Los Angeles store on West Third Street.

[19] The new authorization coincided with preparations for a move to the California Theater, broadcasting live music, with Fred Christian continuing as station manager.

[20] On June 12, 1922, the Los Angeles Times reported that "After more than two months of preparation, the new broadcast station at the California Theater had its opening program Saturday evening at 9:15, sending out a wavelength of 510 meters [588 kHz].

The Express made significant upgrades, including increasing the power to 500 watts, and began broadcasting from the Paul G. Hoffman Studebaker building in Hollywood.

It remained on this frequency until November 11, 1928,[27] when the station was reassigned to 1050 kHz, under the provisions of a major reallocation resulting from the Federal Radio Commission's (FRC) General Order 40.

In early 1928, Guy Earle sold his share of the Evening Express newspaper and reorganized KNX as the Western Broadcast Company.

[20] In 1929, Earle moved the KNX studios to the Paramount Pictures lot,[20] signing a five-year contract, and the station's transmitter power was upgraded from 500 to 5,000 watts.

In 1933, the station moved its studios to the former Peerless Motor Company building at 5939 Sunset Boulevard in Hollywood,[28][29][11][30][31][32][33][34][35][36][20] after being granted permission by the FRC on June 7, 1932, to raise its output to 25,000 watts.

Legendary performers from the "Golden Age of Radio" used KNX studios for their national broadcasts, included Jack Benny, Bing Crosby, George Burns, Edgar Bergen and Gene Autry.

TV situation comedy star Bob Crane was KNX's morning host between 1957 and 1965 at the same time he was appearing as a featured supporting player on the ABC television network series The Donna Reed Show.

KNX was a strong competitor in the Los Angeles market while Bob Crane was its morning personality, but began declining in popularity after he left to star in the CBS television series Hogan's Heroes.

[citation needed] In August 2005, KNX moved out of Columbia Square after operating there for 67 years, and began broadcasting from new studios in the Miracle Mile district on Wilshire Boulevard.

KFWB's format change to news-talk in September 2009 left KNX as the only all-news outlet in the Los Angeles area, which is now emphasized in its alternate slogan, "Southern California's only 24-hour local news & traffic station".

While CBS shareholders retained a 72% ownership stake in the combined company, Entercom was the surviving entity, separating KNX from KCBS-TV and KCAL-TV.