Traditionally, only the Star Spangled Banner was sung at games. On certain major occasions, and especially since September 11, God Bless America has been added. In baseball, it has often been sung during the seventh innig stretch. In football, it is usually at haftime.
bmac may remember that the Philadelphia Flyers had Kate Smith sing "God Bless America" instead of the "Star Spangled Banner" before games on occasion for good luck. Kate Smith was the singer who made "God Bless America" popular in the early 1950's.

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