Advertising Postcards

This is an advertising postcard for Green River Whiskey.

Usually, advertisements for Green River Whiskey came in the form of tokens, not postcards. However, the icons are the same: a horse laden with a jug of whiskey, being led by a man of African-American descent. The statement at the bottom is the slogan for the brand, "She was bred in old Kentucky." This could refer to both the horse and the whiskey. In addition, the whiskey was said to be "The Whiskey Without a Headache."

Why would the man be transporting whiskey jugs by horse? What does this tell you about the society and culture during this period?