Where did horses with these distinctive gaits come from? Do you know the origins and if it was found wild or was it somehow created and bred into them?
From the Tennessee Walking Horse Home page:
It is a composite breed that evolved from the Narragansett Pacer, Canadian, Morgan, Standardbred, Thoroughbred and American Saddlebred...
I think the "ambling gait" is a naturally occuring thing that was selectively bred into quite a few breeds. The original Appaloosas used to be known for it too before the US Army exterminated most of them. There was something called a "Spanish Jennett" that I don't think exists anymore that is in the foundation breeding of alot of these horses.