It depends on what you count as 'soda', but the usual answer is Vernors, the Detroit ginger ale. James Vernor, a pharmacist, created it in 1866 and the company says it was first sold that year. Vernors still ages its ginger ale in oak barrels, and the company has kept the recipe in production since then.
If you mean the oldest American soft drink brand still sold, the strongest rivals are from the 1870s:
- Moxie: Dr. Augustin Thompson introduced it in Lowell, Massachusetts, in 1876, first as a medicinal tonic called Moxie Nerve Food. The company itself calls it one of the oldest soft drinks in the country.
- Hires Root Beer: Charles Hires sold his root beer extract from 1876, and it was promoted at the Philadelphia Centennial Exposition that year.
Some of these claims are marketing claims that have never been settled by a single historical authority, and early mineral-water and soda-fountain drinks predate all of them. The 1866 date for Vernors is the company's own; the 1876 dates for Moxie and Hires are also company and trade-history accounts. If you want to check them, the company histories and period newspaper advertisements are the place to start.
