If you attend a baseball game today, during the seventh inning stretch you’re likely to hear the entire stadium sing, “Take Me Out to the Ball Game.” We’ve grown so accustomed to singing the song during ballgames that it feels like the ritual has been around forever, but if it wasn’t for a device called the magic lantern, first-wave feminism, and a sportscaster named Harry Caray, our familiar custom wouldn’t exist. This is the story of how a simple Tin Pan Alley ditty embedded itself in baseball tradition.