What was the first national event covered by a radio station?
The first national event covered by a radio station was the 1921 Baseball World Series.
The first national event covered by radio was also the first "subway series" in NY as the New York Giants (now the San Francisco Giants) played the New York Yankees. This was also the first time the New York Yankees appeared in a World Series of Baseball.
The game was covered live by KDKA radio of Pittsburgh. It was announced by Grantland Rice.
The game was also rebroadcast by WBZ in Massachusetts.
Addiitonally, announcer, Tommy Cowan also recreated the games over the Westinghouse-owned station WJZ out of Newark NJ. He announced it as he listened to reports phoned-in from the stadium by a colleague.