The Spanish developed what we now consider the cowboy tradition, 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 has access to vast amounts of land that provided 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. During the 16th century, the Conquistadors and other Spanish settlers brought their cattle-raising traditions as well as their horses and cattle to the Americas. They started with their arrival in what today is Mexico and Florida.

The arrival of horses was particularly significant, as equines had been extinct in the Americas since the end of the prehistoric ice age. However, horses quickly multiplied in America and became crucial to the success of the Spanish and later, settlers from other nations. The earliest horses were originally of Andalusian, Barb and Arabian ancestry. A number of uniquely American horse breeds developed in North and South America through selective breeding and by natural selection of animals that escaped to the wild. The Mustang and other colonial horse breeds are now called "wild," but in reality are feral horses — descendants of domesticated animals.

Thus, though popularly considered as a North American icon, the traditional cowboy actually comes from a Hispanic tradition. The traditional cowboy evolved further in the Central States of Mexico, Michoacan, as well as areas to the north that later became the Southwestern United States. The Mexican cowboy would eventually be known as "charro."

Before the Mexican American War in 1848, New England merchants who traveled by ship to California encountered both hacendados and vaqueros, trading manufactured goods for the hides and tallow produced from vast cattle ranches. American traders along the Santa Fe Trail had similar contacts with vaquero life. Starting with these early encounters, the lifestyle and lingo of the vaquero began a transformation which merged with English cultural traditions and produced what became known in American culture as the "cowboy".