This article is from the Dr. Pepper FAQ, by Christopher Flaherty with numerous contributions by others.
You can either:
a) Visit the plant in Dublin, Texas--the oldest Dr Pepper bottling
plant in the world and the only plant in the U.S. which is allowed by
the Dr Pepper corporation to still manufacture the soda with cane
sugar. The Dublin Dr Pepper Bottling Company is located at 221 South