|CBC Radio began in 1936, and is the oldest branch of the Corporation. In 1949, the facilities and staff of the Broadcasting Corporation of Newfoundland were transferred to CBC upon Newfoundland and Labrador's entry into Canadian confederation.
Beginning in 1944, the CBC operated two English language radio services: the original network became the Trans-Canada Network, and a second network, the Dominion Network, was established with CJBC in Toronto as its flagship. With the exception of CJBC, all 35 stations on the CBC Dominion Network were privately owned affiliates. Its programming tended to be lighter than that of the Trans-Canada Network, carrying more American programming in its schedule. As well, the Dominion Network operated only in the evenings, freeing affiliates to air local programming during the day.
In 1962, the Dominion Network was dissolved and within a few years CJBC became a French-language station broadcasting the programming of Radio-Canada.
In 1960, the CBC began running distinct programming on its three existing FM English language stations, which were previously providing simulcasts of programming on its AM stations. The stations, located in Toronto, Ottawa and Montreal, broadcast a monoaural FM signal. Programming consisted mostly of classical music. The stations were linked by CN/CP Telecommunications via land-line and microwave. This service was discontinued in 1962, but resumed in 1964 in stereo. Eventually, a national satellite-distributed network of stereo FM stations was established. In 1975, the FM network was branded CBC Stereo, and the AM service was designated CBC Radio.
CBC Radio stopped running commercial advertising in 1974. Until 1995, the network signed off the air between 1 a.m. and 6 a.m. daily — in that year, it launched an overnight program, CBC Radio Overnight, which airs international news and documentary programs from the World Radio Network.
In the 1990s, many of the CBC's AM stations moved to FM, meaning that the old distinction between the AM "Radio" network and the FM "Stereo" network was no longer accurate, even though many of the FM "Radio" stations broadcast in mono only. As a result, in 1997 the services were rebranded with CBC Radio becoming CBC Radio One and CBC Stereo becoming CBC Radio 2. Although several Radio One stations still broadcast on AM as of 2008, most also have FM rebroadcasters in major urban centres within their broadcast area, due to issues with urban reception of AM signals.
Accessed 12.08.2009 from http://en.wikipedia.org/wiki/CBC_Radio_One