IMO, the canary in the coal mine was September 1, 2001 when Disney bought WEVD, a small but influential AM radio station with great reach airway wise. WEVD was a progressive, liberal talk radio station. It had 4-5 hosts who tackled issues in the boroughs of NYC, New York State, nationally, and internationally. Topics that haven't been examined since its demise.
The Jewish Forward had owned the station since it was created in 1927, named after Eugene V. Debs. Its former programming had been shows in different languages to allow immigrants to assimilate, but in their own languages.
From 1998 to August 31, 2001, WEVD had interviews with democratic politicians, columnists (local and national), newsmakers, etc. The public was well-informed. And it attacked Mayor Rudolph Giuliani where warranted. It had better news than the two tabloids without pushing an agenda.
When it was announced that The Forward sold WEVD (supposedly to finance its newspaper), many grieved. Not just for the obvious reasons. WEVD had a notably sized audience of seniors who remembered and lived through The Great Depression, Hitler, the Second World War, FDR, the New Deal. They were actively engaged. Now they were rendered silent.
During WEVD's last years, two other radio stations weren't RW (yet), WABC and WWOR. These formats reflected the demographics of New York City. Now all are gone, save for Pacifica on the FM dial, WBAI. (I'd include NPR affiliates in NYC, but they're rather watered-down.)
Air America came and went. And now there really isn't any non-RW radio on the AM dial. In 2001, I decried WEVD being sold and converted to WEPN, a radio affiliate of ESPN. I was told it was a commercial decision. But I knew better that the big guns were coming after non-RW radio. I wish I were wrong.