The origins of the cowboy tradition come from Spain, beginning with the hacienda system of medieval Spain. This style of cattle ranching spread throughout much of the Iberian peninsula and later, was imported to the Americas. Both regions possessed a dry climate with sparse grass, and thus large herds of cattle required vast amounts of land in order to obtain sufficient forage. The need to cover distances greater than a person on foot could manage gave rise to the development of the horseback-mounted vaquero.

Various aspects of the Spanish equestrian tradition can be traced back to Islamic rule in Spain, including Moorish elements such as the use of Oriental-type horses, the la jineta riding style characterized by a shorter stirrup, solid-treed saddle and use of spurs, the heavy noseband or hackamore, and other horse-related equipment and techniques. Certain aspects of the Arabic tradition, such as the hackamore, can in turn be traced to roots in ancient Persia.

During the 16th century, the Conquistadors and other Spanish settlers brought their cattle-raising traditions as well as both horses and domesticated cattle to the Americas, starting with their arrival in what today is Mexico and Florida. The traditions of Spain were transformed by the geographic, environmental and cultural circumstances of New Spain, which later became Mexico and the Southwestern United States. In turn, the land and people of the Americas also saw dramatic changes due to Spanish influence.

More Info: en.m.wikipedia.org