Root beer is a carbonated, sweetened beverage, originally flavored with the root of a sassafras plant (or the bark of a sassafras tree). At one point this ingredient was banned, as the oil in it is harmful to humans. Root beer may contain alcohol.
Root beer was first sold as a commercial drink in 1876 by Charles Hires. In 1919, Roy Allen started selling A&W Root Beer - the top-selling brand today.