The Mustang has its roots in Spain and still today carry many of the characteristics of the influence of their Spanish descendants. The Mustangs in the United States were the mounts of ranchers, Indians and soldiers and were the foundation for many of our American breeds. The Spanish conquistadors brought the Mustang to America during the 16th century. Due to horses escaping into the wild in the western United States and other regions the mustang is a combination of many different breeds.
Some traits however stay the same.
One of the most predominant though is the dorsal eel-like stripe that run down the back of those from Spanish origin. Soon the wild horses of the US would breed with others, those lost or set free in the wild and as a result the mustang is known to have crossbred with other breeds such as quarter horses, drafts, Arabians, and who knows what else. By the 1900s the wild horse numbers had risen to more than two million. Two major problems plagued the Wild Horse aside from disease, starvation and the environment. These two problems in the Mustang history would lead to their slaughter.