Both in the early California Vaquero period, starting as early as the late 18th century, as in the later Texas cowboy culture with its iconic cattle drive period after the civil war until about the turn of the 19th century, there was no existence of western horse breed registries.
The Vaquero period was dominated by horses of Spanish descent—horses that accompanied the Spanish on their explorations and colonizations of the west. The Spanish brought Andalusian horses, barb descendants, also known as Iberian horses, to the area that's modern-day Mexico. As California was explored and colonized via a mission system, the Spanish explored their upward colonizations on horseback from modern-day Mexico way up north. The mission system was connected with missions at one-day travel horseback from each other.
The later Texas period combined horses of Spanish colonization descent that populated Texas because of Alonso de Léon's colonization methods that included natural horse and cattle breeding. These horses were enriched by an influx of Morgans, Thoroughbreds, and other breeds.
Although Texas was mainly a resource to provide horses for the American Civil War, this event also caused an influx of horses. Also, the cattle drives as such brought horses from other areas. Cowboys often returned with other horses than where they left with.
- Vaquero's rode mainly Andalusian/Barb descendants and their crosses
- Texas-style Cowboys rode the following breeds and their crosses) Spanish/Barb descendants, thoroughbreds, Morgans, English stock horses, American Saddlebred, Arabians, Chickasaw ponies, and Mustangs (which contain many of these breed influences, and are a result of nature's selectivity as a consequence of their feral charter)
Today, the most widespread cowboy culture is the Texas-style cowboy. The preferred horses are Quarter Horses, Paints, Appaloosa and their crosses. The vaquero (Buckaroo) culture is still more oriented toward the types of Quarter Horses/Thoroughbred/Vaquero Horse with Spanish (Iberian) characteristics and appearance
