"WJZ-TV(Channel 13) was originally an ABC affiliate; it was the second primary affiliate of the fledgling network. Until 1956, it carried a secondary affiliation with the DuMont Television Network, and originated many Baltimore Colts games for DuMont. The Westinghouse Electric Corporation purchased WAAM in 1957 and renamed it "WJZ-TV". The WJZ call letters had previously resided on ABC's flagship radio/television combination in New York City, which changed its calls to WABC-AM-FM-TV in 1953. However, Westinghouse's history with that set of call letters went back even further, as it was the original owner of WJZ radio, the flagship station of NBC's Blue Network, which would eventually become ABC."

-Wikipedia