CKGW and CBL

CBLA's origins date back to March 5, 1928. That was the official sign on of CKGW at 910 AM, a commercial station owned by Gooderham and Worts, with studios at the King Edward Hotel.^[3] However, Gooderham & Worts had been operating the station on an experimental basis from as early as 1925.^[4]

Due to the instability of frequency allocations in North America at the time, the station's dial position changed several times over the next number of years, to 960, 690 and finally clear channel 840. In 1932, the station was leased by the CBC's predecessor, the Canadian Radio Broadcasting Commission. It used the call sign CRCT until 1937, when the station was purchased outright by the CBC and adopted the call letters CBL. It moved to a new transmitter facility in rural Hornby. The 650 ft guyed mast that the station transmitted from was for many years the tallest structure in all of Canada.^[5]

740 AM

With North American Regional Broadcasting Agreement (NARBA) in 1941, the station moved to 740 kHz. Its former channel, now 860 kHz, went to CFRB (which would relocate to 1010 kHz in 1947), while the 840 kHz clear channel was relocated to Louisville, Kentucky, where it was taken by WHAS. (See Canadian allocations changes under NARBA.)

Between 1938 and 1943, CBL had a rebroadcaster, CBY, to supplement coverage in Toronto. CBY broadcast on 960 kHz, switching to 1420 in 1939 and then to 1010 in 1941. CBY is now CJBC 860, Toronto's Ici Radio-Canada Première French language station.

99.1 FM

In 1946, CBL-FM was launched, bringing the CBC's FM network (now known as CBC Music) to Toronto. It originally broadcast on the same 99.1 MHz frequency now used by CBLA, but moved to 94.1 in 1966. 99.1 was vacant until 1977, when it was assigned to the CKO radio network. CKO ceased operations in 1989, and the frequency was again vacant until it was assigned to CBLA.

CBL established a large low-power relay transmitter (LPRT) network in Northern and Central Ontario during the 1950s and '60s. These transmitters, all on AM frequencies, mainly rebroadcast the CBL signal but also offered some separate regional programming directed towards the regions served by the LPRT network in place of some local Toronto programming. One example of this was the daily Northern Ontario Report, which aired in the late afternoon. Most of these LPRT network transmitters now rebroadcast CBCS in Sudbury or CBQT in Thunder Bay. Some of these transmitters have switched to FM as well, or have been shut down as FM transmitters covering areas served by multiple AM transmitters have signed on.

In 1997, CBL applied to the Canadian Radio-television and Telecommunications Commission for conversion to FM. 740's daytime signal easily covered Buffalo, New York; Erie, Pennsylvania and Youngstown, Ohio. It was also powerful enough to serve as the CBC outlet for the Waterloo Region as well. Its nighttime signal reached much of the eastern half of North America (including three-fourths of Canada). However, radio frequency interference made the station nearly unlistenable in some parts of downtown Toronto. In a controversial decision, the CBC was awarded the 99.1 frequency^[6] over Milestone Radio, which had applied to open an urban music station, and which would have been the first station operating under that format in Canada, to serve the city's large black community. Adding to the controversy of the CBC being awarded a station on the FM band in the country's biggest market, 99.1 was believed at the time to be the last available FM frequency in the city. On April 19, 1998, the new FM signal signed on for the first time, and began simulcasting CBL.

On June 18, 1999, the station completed its move to FM, adopting the CBLA call letters. CBL 740 remained in operation for an additional day, broadcasting a recorded loop listing alternative FM frequencies for any remaining listeners. The final announcement ran thus:

This is CBC Radio One, broadcasting from the Hornby transmitter at 740 AM. In the Toronto area, we will now move to 99.1 FM, with additional frequencies throughout southern Ontario. This transmitter has served the community well since 1937, and has been at 740 AM since 1941. This is the end of an era in Canadian broadcasting history. Now, signing off, from CBL, adieu.

— Philip Savage, CBC Communications department^[7]

Relay transmitters and HD Radio

The CBC subsequently surrendered two relay transmitters outside the city which duplicated the CBLA signal. In 2000, the CRTC awarded one of the new frequencies thereby available in Toronto to Milestone, which launched CFXJ in 2001, and the other to the Aboriginal Voices Radio Network, launching CFIE-FM in 2002; that frequency later became home to CFPT-FM. The Hornby transmitter was leased to the new occupant of 740, CHWO, in 2001. That station is now known as full-service oldies station CFZM.

The CBC Jarvis Street Tower site was demolished in 2002 to make way for the RadioCity condominium development.

On October 4, 2021, CBLA added HD Radio operations, as part of upgrades in Toronto, Ottawa and Vancouver.

Former rebroadcasters

• Kitchener-Waterloo - CBLA-FM-2 89.1 - A former repeater of CBLA-FM what is now a local CBC Radio One outlet serving the Kitchener-Waterloo region.

Shortwave relay (VE9GW/CRCX)

Gooderham & Worts opened an experimental shortwave radio station in April 1930 with the call letters VE9GW. Listed as being located at Bowmanville, Ontario, at CKGW's transmitter site, it relayed CKGW programming on 6095 kHz to northern Ontario, northern Manitoba and the Canadian Arctic. While mostly relaying programming from CKGW, it would also air a regular specialty programme for DXers in the International Short Wave Club. After switching to a new transmitter in the winter of 1930-1931, the station boosted its power to 200 watts from 25 Watts and it could be received as far away as Europe, South Africa, and New Zealand on either 6.095 or 11.81 MHz, and would later broadcast on 24.38 MHz, as well. In 1932, the station's power increased to 500 watts. From 1933 to 1936, CKGW and VE9GW were leased from Gooderham & Worts by the Canadian Radio Broadcasting Commission, which used the station as one of the broadcasters of Northern Messenger, a mailbag programme aimed at listeners in the Far North, which the CBC would continue to air into the 1970s. CKGW became CRCT and, in 1935, VE9GW's call letters changed to CRCX. In 1937, both stations were purchased by the new Canadian Broadcasting Corporation. CRCT became CBL and CRCX was closed down in 1938. The station mostly broadcast on 6.095 MHz but, at various times, transmitted on 11.81 or 24.38 MHz.^{[23][24][25][26][27]}