Bourbon is the native spirit of the United States - similarly to how whiskey is the native drink of Scotland. While bourbon today is produced in almost every country in the world, you need to visit the Bourbon trail if you really want to experience the world's best and finest. The spirit traces its origin back to Kentucky, which is the original birthplace of the famous drink.
The Bourbon Trail is sometimes called the Kentucky Bourbon Trail, as most of the distilleries and bars are located in this US state. The trail was founded by the Kentucky Distillers' Association, as a way to promote the bourbon industry. That's a pretty smart move, as most people want to experience new things, and connecting drinking with tourism makes sense to a lot of world travelers.