On this day in 1941, the penalty flag was first introduced into the game of football in the U.S.A.. Before the penalty flag, referees used horns and whistles to indicate an infraction, but the problem was that the fans didn't know that the game stopped because of a penalty.

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Here's the story according to ysusports.com/fan:

"In the game of football, a penalty flag is thrown when a rules infraction occurs during a game. The creation of that penalty flag was in Youngstown, Ohio nearly than 60 years ago.

It was created by former Youngstown State University coach, Dwight Dike Beede on Oct. 17, 1941. The flag was first used in a game against Oklahoma City University at the Youngstown's Rayen Stadium. Today the penalty flag is used in every competitive football game throughout the world.

Beede came up with idea of the flag and had his wife sew it together. His wife, Irma Beede, later became known as the 'Betsy Ross of Football' because she sewed the first flags together.

Two of the original flags are on display in Mosure Hall on the fourth level in Stambaugh Stadium."