The opening words to the national anthem are familiar to anyone who watches or attends a sporting event in the United States. But why is the national anthem played at games to begin with? Depending on one's point of view, you can blame - or thank - World War I for being the catalyst for this tradition. "The Star-Spangled Banner" began its life as a poem by Francis Scott Key about seeing the flag flying over Fort McHenry after it was bombarded by British troops in 1814. Long before it became the official US national anthem in 1931, the song was recognized for its ability to boost patriotism.