General Tire bought the Yankee net in 1947, and the Don Lee net in 1950 including their large share of Mutual Stock. They started buying the individual stations in 1951, starting with WOR.IIRC, the only network that RKO-General owned/operated, at least in the New England states, was the venerable Yankee Network, whose flagship station was the old WNAC 680 Boston, but that ceased operation in 1967 when WNAC passed on and became The Big 68 WRKO. RKO-General may also have had some holdings in the now-defunct Mutual Broadcasting System, whose flagship was WOR 710 New York. How times have changed.
Mutual was a major affiliate owned operation, and by buying Don Lee, Yankee and WOR, they became a majority owner of Mutual. They later bought out the WGN shares, along with those of the WHK parent (the Plain Dealer) and CKLW to completely own it. They also bought CKLW and WNAC in the process of this multi-year consolidation, which also added Don Lee affiliates KFRC and KHJ.