Which breed is known for having its origins in the Southern United States?

The American Saddlebred is a breed that originated in the Southern United States, specifically in Kentucky during the late 18th century. This breed was developed primarily for its versatility and smooth gaits, which made it ideal for use in both riding and driving. The American Saddlebred is particularly known for its comfortable ride and has become associated with various forms of equestrian sport, as well as pleasure riding.

In contrast, the other breeds mentioned have different origins. The American Bashkir Curly is believed to have roots in the United States but specifically relates to certain domesticated horses from the Bashkir region and does not have a distinctly Southern origin. The Clydesdale is a breed that hails from Scotland, primarily known for its strength and size as a draft horse. Thoroughbreds are also not of Southern origin; they were developed in England and are famous for their speed and agility in horse racing. Each of these breeds has its unique history and geographical roots, making the American Saddlebred the correct choice in relation to Southern U.S. origins.