From Wikipedia:

The Barq’s Brothers Bottling Company was founded in 1890 in the French Quarter of New Orleans, by Edward Charles Edmond Barq and his younger brother, Gaston. The Barq Brothers bottled carbonated water and various soft drinks of their own creation. Early on their most popular creation was an orange-flavored soda called Orangine, which won a gold medal at the 1893 World’s Columbian Exposition World’s Fair in Chicago, Illinois.

Edward Barq moved to Biloxi, Mississippi, in 1897 with his new wife.

The following year he opened the Biloxi Artesian Bottling Works. 1898 is often given as the debut year for what was later to be known as “Barq’s root beer,” but some sources say this particular product was not produced until some two years later.

For many decades Barq’s was not marketed as a “root beer.” This was in part a desire to avoid legal conflict with the Hires Root Beer company, which was attempting to claim a trademark on the term “root beer.” It was also due to differences from other root beers at the time. The base was a sarsaparilla drink of the style of the late 19th century, in a formulation with caffeine, less sugar, and higher carbonation than other brands, though with less of a foamy “head.” It was decided to market the soft drink simply as Barq’s.

The traditional slogan was the simple affirmation “Drink Barq’s. It’s good.”

For a time it was marketed with the slogan “Is it root beer?” before the company decided to market the product as such.

The Barq’s brand was acquired by the Coca-Cola Company in 1995.