Recently I watched many cowboy movies on Youtube. I then became familiar with gringo, amigo, muchacho, muchachita, and also mister. The latter should no more question as it supposed to be very clear. Unfortunately it is not. Those conversations mostly in the mid of 19th century to the early of 20th century in The United State and Mexico. Many times I heard, if someone saw or met a matured and unknown man, then he (the who saw that matured and unknown man) would call mister rather than to use Sir. For example, a cowboy was riding a horse met a man, then the cowboy would say, "Mister!" of course without mentioning the name as the cowboy didn't know him. In my school, was taught that to call someone in respect we must call Sir if he is quite mature. I used to do it, not to call him with mister. Of course I know how to use word mister, to call someone with his last name or his post, such as Mr. President, Mr. Smith, etc
Then my question, was that calling common in the old time? Or was it just affected by the cowboy culture?