On March 28, 2003 — The commissioner’s office announces teams will pay tribute to the U.S. Armed Forces during the seventh-inning stretch of all home openers by having `God Bless America’ performed. Although the song has been part of all games since the September 11th terrorist attacks, it will be heard only in major league ballparks at the home openers, Sunday, and holidays games.

Source:
National Pastime

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