WFIL-TV was originally owned by Walter Annenberg's Triangle Publications, publishers of "The Philadelphia Inquirer" and owners of WFIL radio (560 AM, and 102.1 FM). The WFIL stations were the flagship of the growing communications empire of Triangle Publications, which owned two Philadelphia newspapers (the morning "Inquirer" and, later, the evening "Daily News"), periodicals including "TV Guide", "Seventeen" and the "Daily Racing Form", and a broadcasting group that would grow to ten radio and six television stations. WFIL radio had been an ABC radio affiliate dating back to the network's existence as the NBC Blue Network. However, WFIL-TV started out carrying programming from the DuMont Television Network, as ABC had not yet ventured into broadcast television. When the ABC television network debuted on April 19, 1948, WFIL-TV became its first affiliate. Channel 6 joined ABC before the network's first owned-and-operated station, WJZ-TV in New York City (now WABC-TV), signed on in August of that year. However, it retained a secondary affiliation with DuMont until that network shut down in 1956.