sentences:  In the late 1920s, network owned-and-operated stations (or "O&O") for radio in New York City began producing live entertainment and news programs, fed by telephone lines to affiliates.These eventually were dubbed flagship stations.When television networks were formed in the United States in the late 1940s and grew during the early 1950s, network-owned stations in New York City became the production centers for programs originating on the East Coast, feeding affiliates of ABC, CBS, and NBC in the eastern three-fourths of the country.