Origins of the Horse in North America
The modern horse (Equus caballus) evolved on the North American continent. Disappearing from this area around 10,000 years ago (end of the Pleistocene epoch), it survived on the European/Asian continent. Horses were brought back to North America by the Spanish in the 1500s.
Stray horses became known as mustangs, from the Spanish word mesteño. The word refers to a farmer's guild (mesta), signifying these animals had no true owner. Modern translations have simplified mesteño into signifying "wild." From the 1600s to the mid-1800s, mustangs ranged throughout the Great Plains in vast herds, sometimes numbering in the thousands.