The stations share studios at 33 Dundas Street East on Yonge–Dundas Square in downtown Toronto, while CITY-DT's transmitter is located atop the CN Tower.

The station went on the air on September 28, 1972, by a consortium led by Phyllis Switzer, Moses Znaimer, Jerry Grafstein and Edgar Cowan, as CITY-TV, branded "Citytv" on Queen Street.

In 1981, the station was sold to CHUM Limited, who retained Znaimer as an executive and moved to its 299 Queen Street West studios in 1987.

For the majority of its early life, CITY-TV operated as an independent station, best known for its unconventional approaches to news and other locally produced programming.

The founding ownership group Channel Seventy-Nine Ltd. consisted of – among others – Phyllis Switzer, Moses Znaimer, Jerry Grafstein and Edgar Cowan.

Multiple Access Ltd. (the owners of CFCF-TV in Montreal) purchased a 45% interest in the station, and sold its stake to CHUM Limited three years later.

On July 12, 2006, CTVglobemedia announced its offer to acquire CHUM Limited and its assets, including the Citytv stations, and related cable properties for $1.7 billion.

[7][8] The Citytv system expanded into Western Canada in 2009 when the Jim Pattison Group signed a deal to carry the system's programming on its stations in Kamloops (CFJC-TV), Prince George (CKPG-TV) and Medicine Hat (CHAT-TV);[9] Rogers signed a long-term affiliation renewal agreement for the Pattison stations in September 2012.

[18] CITY-TV and the Citytv system/network has traditionally pursued a programming strategy targeting hip, young and urban audiences, and featured science fiction series (such as the Stargate and Star Trek franchises) with significant cult followings.

Shortly after its takeover by Rogers, Citytv's long-running Great Movies block was cancelled in favour of running more series.

The station has also produced much more local programming than most other Canadian television stations, including the daily talk show CityLine (hosted first by Dini Petty, then Marilyn Denis, and now Tracy Moore); magazine series such as The NewMusic, Toronto Rocks, FashionTelevision, Life on Venus Ave. and MovieTelevision; and interactive series such as Speakers' Corner.

This is not the first time that a live sporting event has aired on a Citytv station, it also served as the Canadian broadcaster for Monday Night Football along with CBC until its American rights moved from ABC to ESPN, and in Canada to TSN, in 2006.

[22] From 2014 until 2017 (when this portion of the package was acquired by TSN and CTV Two), it also aired Thursday Night Football games in simulcast with CBS.

Toronto Maple Leafs games are typically designated to CBC Television and CBLT during Hockey Night, unless otherwise simulcast.

Among those laid off were longtime 6 p.m. co-anchor Anne Mroczkowski and six reporters (Farah Nasser, Jee Yun Lee, Laura Di Battista, Marianne Dimain, Merella Fernandez and Michael Serapio); Pam Seatle was also dismissed, but returned to the station one month later.