The Mustang is a feral horse found in the western United States. It's derivative in Spanish, the word monstenco, means wild or stray. The horses were originally Spanish breeds, but now there are many breeds that live in different parts of the world. At one time these wild horses became so numerous that the Adopt-A-Horse program was formed as a humane way to get rid of some. Most mustangs still exhibit some Spanish characteristics ,but because of their wild nature the Spanish blood has been diluted.