The Iroquois Theatre Fire was and event that happened a long time ago in Chicago. The fire started when this guy was working back stage and notice a light that was short circuiting but didn't say anything. Then a spark from the light flew off and got the whole place on fire. Most of the doors were locked so people who didn't pay couldn't get in or sneak in so a lot of the exit doors were locked. If the doors weren't locked then a lot more people could have lived. Others just died from being caught on fire or from the lack of air.
Carl Prinzler was supposed to go to that play but didn't end up going for some reason. He heard about what happened and decided to make something so something like this won't happen again. What he made was called the panic bar. This was made for if the door was locked on the outside and you were on the inside then you were able to us and open the door. We see this in many places like the doors at schools, stores, and at a theatre. When he made this it looked nothing like how it does today. But now it's a good thing to have in a public place so people could get out easier.