The Mutual Broadcasting System (commonly referred to simply as Mutual; sometimes referred to as MBS, Mutual Radio or the Mutual Radio Network) was an American commercial radio network in operation from 1934 to 1999. In the golden age of U.S. radio drama, Mutual was best known as the original network home of The Lone Ranger and The Adventures of Superman and as the long-time radio residence of The Shadow. For many years, it was a national broadcaster for Major League Baseball (including the All-Star Game and World Series), the National Football League, and Notre Dame Fighting Irish football. From the mid-1930s and until the retirement of the network in 1999, Mutual ran a highly respected news service accompanied by a variety of popular commentary shows. In the late 1970s, Mutual pioneered the nationwide late night call-in talk radio program, introducing the country to Larry King and later, Jim Bohannon.
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https://en.m.wikipedia.org/wiki/Mutual_Broadcasting_System