"Mustang" is the name given to the feral horses of America which first appeared during the 16th century. The name Mustang derives from the word "mesteth", which means "bank or herd of horses". At one time they existed in huge numbers to the point that they were damaging grazing land for domestic animals.
Widespread killing of the Mustang due to their large numbers resulted in a great reduction in their numbers and not until 1971 were regulations placed for their protection. They now are under federal protection and the standards of the Mustang are said to be improving. The breed possesses a wide diversity of physical characteristics.