Dangar

Answer: During Prohibition, which lasted throughout the 20's and early 30's, alcoholic beverages were effectively entirely banned in the US. Illicit, illegal places (often referred to as a "speakeasy" or "rotgut room") were created where people could drink alcohol on the down low. They were often secret establishments or hidden areas within another business. The secret room in the bar is one such room. The reason there are peepholes in the room is so they could keep an eye out for unwanted company (aka, the police or other authorities) while people illegally drank. If they saw the police coming, they could hide the booze and try to find a way to sneak out.

TedStixon