National Day of the Horse on December 13th encourages people of the United States to be mindful of the contribution of horses to the economy, history, and character of the United States.
The domesticated horse we know today, also known as Equus caballus, was introduced into North America by Spanish explorers. Escaped horses eventually spread across the American Great Plains.
Interestingly, there is a debate about the origin of E. caballus. Recent mitochondrial studies of an ancient horse called Equus lamei suggest that it is equivalent to the modern, domesticated horse. E. lamei once populated North America and died out more than 11,000 years ago. This could mean that E. caballus is technically a native species, and its evolutionary origin is North America.