Was there an age limit for youngsters to drink in the frontier towns? It appears most states and territories didn’t have age laws so if a lad was big enough to belly up to the bar he would be served. Prior to the passage of the Prohibition Act on January 16, 1919, a small number of states lawfully allowed drinking under the age of twenty-one. After Prohibition ended on December 5, 1933, all states had such laws–but they varied, with some setting 18 and others 21 as the minimum legal drinking age.
Anecdotal evidence indicates that most frontier saloons did not allow women (with the exception of the “good time girls”) or kids. These were places for men, and only men.
What constitutes a man? Usually, it was up to the judgment of the proprietor or bartender. It looks like Billy the Kid was in saloons by the time he was 18. Billy Clanton frequently imbibing in saloons when he was a teenager. They were accepted as adults at that point, and so their presence was allowed. It’s likely that kids younger than that–those who were on their own, who worked as cowboys–could gain admittance and be served. But that was at the discretion of the saloon.
One other thing–youth alcoholism was a major reason that Prohibition finally was approved. I haven’t seen good figures on it, but a huge number of kids were hooked before they were 16 (John Wesley Hardin being a great example).
Bartenders were pretty good at judging whether a lad was still wet behind the ears and would act accordingly. Most youths in their early teens were still doing men’s work during the Great Depression so you can imagine how it was 50 years earlier. Come to think of it, I know of some ranch and farm kids today who act more responsibly than most 30-year-old city boys.