Tampa's downtown movie palace, The Tampa Theatre, has stood through boom times and depressions. The jewel still stands along Franklin Street. It has been there since 1926 and was the first commercial building in Tampa with air conditioning.
Back then the movies were a novelty and people would line up, pay 10 cents to get in and then stand in an even longer line to await the departure of another patron.
Then they'd go inside to watch the movie, and stay until they reached the point at which the story began for them and leave. Apparently, this is where the term, "this is where I came in" comes from.