I was reading the back label on a bottle of Stagg. It says that Stagg was one of four distilleries that operated during Prohibition. I was wondering how it was legal for distillieries to operate during Prohibition.

I did a search and there are references by Chuck and Veach to "medicinal whiskey." But I haven't yet found out what medicinal whiskey was or is. So, what were these distilleries doing during Prohibition? And what is medicinal whiskey?