CKAC was officially launched on October 2, 1922, under the ownership of the local newspaper La Presse, as the first ever Francophone radio station in North America.

However, the acquisition was blocked by the Competition Bureau, resulting in the stations instead being sold in 2004, to Corus Entertainment as part of a larger exchange of assets between the two companies.

CKAC became the flagship and provider of talk radio programming to the Corus Québec network, but its newsroom was later shut down in favor of that of its new sister station CINF (later CHMP-FM).

Previous hosts on the station included: Michel Langevin and Gabriel Grégoire (morning show), Mario Langlois (mid-mornings), Jean-Charles Lajoie (early afternoons), Michel Villeneuve (afternoon drive), Jean Chartrand (early evenings), Ron Fournier (late evenings), Marc Bryson (weekends) and Jacques Fabi (weeknights).

(The program disappeared in 1970, as religious practice declined precipitously in the late 1960s, in Montreal and elsewhere in Quebec and ratings were down, but this provoked many complaints among still-devout Catholics).

On March 13, 1958, CKAC raised its power to 50,000 watts full-time, using a directional antenna pointing east using two towers, as it moved to its current transmitter site located in Saint-Joseph-du-Lac, just west of the Island of Montreal.

In the early days of radio in Canada, the CBC used its dual role as regulator and broadcaster to ensure that most of the country's clear-channel allocations went to CBC-owned stations.

However, CKAC quickly regained the top ratings spot in 1970, due to the crucial role its highly regarded news service had in keeping listeners informed during the October Crisis, in which the terrorist and separatist Front de libération du Québec movement kidnapped and murdered provincial Labour Minister Pierre Laporte.

In addition, radio in Quebec was generally suffering from the appearance of the new TQS TV network, which provoked a severe advertising price war.

However the Competition Bureau, another federal agency, partially blocked the deal over concentration of ownership issues, and ordered Astral Media to sell Radiomédia stations, which were temporarily put into trusteeship.

A first attempt failed when TVA (Quebecor) and RNC Media were refused permission by the CRTC in June 2003, to buy the stations, because of ownership concentration concerns.

Jean Lapierre, who was the afternoon drive host, also announced his departure as he returned to active politics; as a result Morin and Chamberland exercised their option to cancel their acquisition, paying a million-dollar fee to do so.

Despite widespread opposition against that deal, the known existence of at least four other serious and much less controversial contenders to buy the Radiomédia stations, and numerous allegations to the effect that Corus Entertainment's offer was actually part of a larger plan to prevent any meaningful competition to its new FM talk radio format (as Corus seemed to try to weaken and steal listeners from CKAC and not from the increasingly popular CBF-FM, and its sales representatives claimed to clients that they would be better advised to buy advertising at CHMP-FM and not CKAC as they pretended the latter was going to close shortly no matter what would happen), the deal was approved in January 2005, by the CRTC in the midst of strong rumours that Astral Media would close CKAC if the deal was not approved.

[8] On April 30, 2010, it was announced that Cogeco will acquire all radio stations owned by Corus in Quebec for $80 million, pending CRTC approval.

This relaunch superseded an application Cogeco had filed with the CRTC earlier in the year to reactivate the former CINF (Info 690) transmitter for a similar format (while maintaining all-sports on CKAC).

Unlike Cogeco's original plans for 690 kHz, CKAC's traffic radio service operates 24 hours a day, with live announcers on the air between 6:00 and 1:00 (non-holiday weekdays are 90' earlier).

[12][13] After playing a wide variety of continuous music over Labour Day weekend, Radio Circulation 730 made its debut at 4:30 am on September 6, as announced.