Smooth-gaited horses, generally known as Palfreys, existed in the Middle Ages, and the Jennet in particular was noted for its ambling gaits. Peruvian Pasos trace their ancestry to these ambling Jennets; as well as to the Barb, which contributed strength and stamina; and to the Andalusian which added style, conformation and action. Horses arrived in South America during the Spanish Conquest, particularly after 1542, when the Spanish created the Viceroyalty of New Castilla. This later became the Viceroyalty of Peru, an important center of Spain's New World colonies in the eighteenth century. Once in Peru, they were used primarily for transportation and breeding stock. In the north of Peru, the vast size of sugar and cotton plantations meant that overseers needed to travel long distances, often taking days to cross the plantation. In the south of Peru, the arid deserts that separated settlements required sturdy, strong horses. In both cases, smooth-gaited horses with good endurance were required. On the other hand, Peru did not develop a livestock-based economy, and thus did not need to breed for the speed or agility characteristic of stock horses.