The First Coast-To-Coast World Series Broadcast
Both NBC and CBS were granted permission to air the 1927 World Series:
That probably seems odd by today’s standards, but it wasn’t so strange back then. In fact, for a few years starting in 1935, the World Series was broadcast on no fewer than three radio networks.
But the thing that was so special about the 1927 World Series broadcast is the large reach that the NBC and CBS chains had:
In fact, it seems that additional networks joined onto the chain right before the series opened:
I believe that would maket he 1927 the first official coast-to-coast baseball broadcast.
Now, it’s not like the entire country was within reach of those radio waves. In Alabama, for example, it seems that local radio presented a recreated play-by-play account:
Now, the most fun part about the old days of radio are some of the old radio advertisements:

It was a big deal back then.
Crosley Radio Dealers is the same family that owned the Reds until just before winning the pennant in 1961
That’s how Ronald Reagan got his start, by re-creating baseball on the radio